Ribbis: Reasons and Rationales

R. Yair Hoffman writes:

[L]et us try to provide some philosophical explanation for the underlying prohibition of Ribis. Imagine the following scenario:

The family lives in the old country. The eldest son has emigrated and has made it to New York and has an apartment in the Lower East Side of Manhattan. Another son is about to seek his fortune in New York and needs a place to stay. He arrives at the brother’s house. The brother tells him, “Look, brother, you can stay in my apartment, no problem. And I will even charge you less than the Motel Six rates. It will only be $40 per night!” The parents would certainly be upset at their eldest son’s behavior. This is not the way one behaves with a brother.

ONE FAMILY

By the same token, the Torah views all Jewish people as one family. When a brother or sister needs a loan, therefore, we do not charge them interest, just as we would not charge them rent when they stay by us. Indeed, there are six prohibitions in the Torah associated with charging interest. The prohibition is called “Ribis” interest or “Neshech.” Anyone who has ever taken out an interest bearing loan can appreciate the fact that Neshech comes from the Hebrew root word, “bite.” Interest payments certainly do feel like a serious snake bite.

I do not understand this at all: by this logic, the Torah should have prohibited the charging of rent for residential property!

My friend and colleague H.S. cites this sort of rationale in the name of R. Shimon Schwab:

In Parshas Behar, the Torah forbids us to charge another Jew interest. It is not only prohibited for a lender to assess interest, but a borrower is also forbidden to voluntarily pay it. The commentaries have grappled with the rationale for this prohibition. Is there something wrong with charging interest when both parties agree? If one is permitted to charge a rental fee for the use of that person’s car for a week, why can’t one charge a “rental fee” if someone wants to have use of that person’s money for that same amount of time?

Rav Shimon Schwab offers the following explanation: Indeed, in the world of business, interest has its place. A functional economy relies on loans, which are only likely to occur if interest may be charged. In the realm of family, however, interest does not belong. Imagine if your brother or sister needed a loan and, despite having the money readily available, you would only offer the loan with interest! Such an action would be distasteful and inappropriate. The Jewish people, explains Rav Schwab, are all one family. The Torah stresses this by describing the impoverished person as “your brother” and instructing us to let our “brother” live along with us. As long as we view our fellow Jews as family, loans will be granted willingly without the need or desire to charge interest. Our Parsha describes a number of scenarios in which a Jew may become impoverished and need assistance to resolve his situation; in each case, the Torah describes him as “your brother.” If we can successfully adopt this perspective and always view our fellow Jews as our brothers and
sisters, then – like any close-knit family – we will be there for each other in times of need and be prepared to offer assistance without desire for compensation.

But once again, this argument proves far too much:

Imagine if your brother or sister needed a place to live and, despite having a suitable residence readily available, you would only offer it to him at market rent! Such an action would be distasteful and inappropriate.

Incidentally, R. Schwab’s great predecessor, R. Samson Raphael Hirsch, while agreeing with the basic premise that charging interest is not inherently immoral, understands the rationale for the prohibition quite differently:

“I would like to close by sharing with you a thought from Rav Samson Raphael Hirsch about the reason why the Torah prohibited interest. He notes that if the Torah considered charging interest to be inherently immoral, it would have banned charging interest from non-Jews, and also would have prohibited only the lender and not the borrower. Rather, Rav Hirsch notes, the Torah’s prohibition is to demonstrate that the capital we receive from Hashem is so that we donate tzedakah and provide loans, and thereby fulfill our share in building and maintaining a Torah community. The Torah’s goal in banning the use of capital for interest-paying loans is to direct excess funds to chesed and tzedakah.”

Once again, however, this explanation fails to distinguish between loaning money at interest and other forms of investment. Why is making an equity investment in a business any more legitimate than investing in the same business by lending it money at interest?

The truth is that it is really quite difficult to offer a rationale for the prohibition of charging interest that will be completely satisfying to the modern mind, as I discuss in my weekly halachah column for this past פרשת בהר:

In parashas Behar (25:36-37), the Torah forbids usury. The prohibitions against usury, as well as reprobation of the usurer and approbation of he who avoids usury, are reiterated throughout the Bible (Shemos 22:24; Devarim 23:20-21; Yechezkel 18:13,17; Tehillim 15:5). The Torah never explains, however, why usury is prohibited. A number of rationales have been proposed, although none appear entirely satisfactory:

  • Shaarei Yosher (end of Shaar 5) explains that usury is actually a form of theft. Despite the fact that the borrower willingly accepts the interest obligation, his consent is considered to have been given erroneously, since we presume that he does not fully realize the harm that he is thereby inflicting upon himself. This would not seem to apply, however, to loans with reasonable interest rates that are clearly beneficial to the borrowers, such as prime mortgage loans taken out by homebuyers.
  • Radak (Tehillim ibid.) declares that an agreement to pay interest is tantamount to a contract entered into under economic duress, since the borrower needs the loan. It is difficult to understand, however, why such an agreement is different from any other contract. E.g., a tenant only agrees to pay rent since he needs a place to live!
  • Some suggest that since there is a mitzvah to lend money to one’s fellow Jew, the charging of interest is forbidden under the general prohibition against charging for the performance of a mitzvah (see Shut. Avnei Nezer YD 159:3). This rationale would not seem to apply, however, with regard to money that the lender would otherwise be investing for profit, since the prohibition against charging for the performance of a mitzvah contains an exception for the recouping of opportunity costs entailed by such performance (cf. Bris Yehudah Ch. 1 n. 10).
  • Some suggest that since interest is too reliable a source of income, it eliminates the need for bitachon (reliance) upon Hashem (Kli Yakar Vayikra ibid.; Introduction to Klala De’Ribisa). The idea that taking advantage of the best available opportunities to better one’s lot can be inconsistent with bitachon is, however, a controversial one (see Commentary of Rambam to the Mishnah, Pesachim 56.; Akeidas Yitzchak #26 p. 221).

My weekly parashah lectures for פרשת בהר on this topic, and accompanying handouts, are available at the Internet Archive.

Avoiding צרעת Like the Plague

Artscroll declares:

For hundreds of years, the popular translation of צרעת [tzaraas] has been “leprosy,” and it was commonly accepted that prevention of the disease’s spread was the reason for the quarantine of a suspected victim of tzaraas and the exclusion from the camp of a confirmed מצורע [metzora], the person smitten with the malady. R. Hirsch demonstrates at length and conclusively that both of these notions are completely erroneous. Very briefly, he shows that the symptoms of tzaraas, as outlined in our Sidrah, are far different from those of leprosy. Furthermore, if the reason for the metzora’s confinement is to prevent contagion, then some of the laws would be ludicrous. For example, if the malady covers the victim’s entire body (13:13), he is not tamei, but if his skin begins to heal, he becomes tamei. In the case of a house that is afflicted (14:26), the Torah prescribes that before the house is pronounced tamei, all its contents should be removed, because they would become contaminated if they were left inside at the time of the pronouncement. But if there were a danger of contagion, it would be irrational for the afflicted household items to be excluded from the quarantine! In perhaps the most telling example, the Talmud teaches us that if the symptoms of tzaraas appear on a newlywed or during a festival season, the Kohen does not examine the affliction or declare it to be tamei, in order not to interfere with the celebration. But if the purpose of these laws is to prevent the spread of disease, it would be absolutely imperative to enforce the laws at times of great overcrowding and mingling!

Clearly, as the Sages teach, tzaraas is not a bodily disease, but the physical manifestation of a spiritual malaise, a punishment designed to show the malefactor that he must mend his ways. The primary cause of tzaraas is the sin of slander. As the Sages say, the word מצורע is a contraction of מוציא שם רע, one who spreads slander (Arachin 15b). Similarly, the Sages teach (ibid. 16a and various Midrashim) that the affliction is a punishment for the sins of bloodshed, false oaths, sexual immorality, pride, robbery, and selfishness. The pattern that emerges is that it is a Divine retribution for the offender’s failure to feel the needs and share the hurt of others. G-d rebukes this anti-social behavior by isolating him from society, so that he can experience the pain he has imposed on others – and heal himself through repentance.1

To be fair to Artscroll, this is indeed an accurate synopsis of Rav Samson Raphael Hirsch‘s treatment of the topic:

No part of G-d’s Torah can serve, as much as this chapter on נגעים, to show the absolute folly of the erroneous idea of “the tendency of the Laws of Moses to be rules and regulations to be enforced for health and sanitary purposes”. On the surface, there are certainly sufficient facts in this chapter to give rise to such an illusion. Clearly it deals with diseases, with a disease which had always been (until quite recent times at least. I.L.), been considered contagious; those affected have to be isolated; for what purpose if not to prevent contagion; this sufficed to fix the character of these laws of Negaim as being sanitary health regulations and to stamp the functioning priests who administered them as doctors. And if, out of the whole register of human pathological diseases just this illness, “leprosy”, alone was picked out for these “police” regulations evidently it must have been just this disease, the most horrible one, from which the Jews mostly suffered, and the fairy tale of Tacitus that it was because of their leprosy that the Jews were driven out of Egypt, can not be so entirely without foundation!

But let us just look at these laws in their most prominent details and see if it even possible to give them any sanitary character.

Already the fact that real leprosy, שחין, in itself is not מטמא at al, the “evil” leprosy, the “incurable Egyptian leprosy, שחין מצרים, שחין רע אשר לא תוכל להרפא, does not bring any state of טומאה, as it says in v. 18 of our chapter that the נגע טמא can only arise in שחין ונרפא, when the leprosy has already begun to heal and healthy skin has already formed over it; and the fact that the outbreak of the “leprosy” over the whole of the body, מראשו ועד רגליו, brings טהרה (v. 12 & 13) – which the “health theorists” take to be a sign that a violent acute attack which covers the whole body indicates a prompt immediate healing, and yet שחין מצרים, the very worst type of case, אשר לא תוכל להרפא, which has no cure is described as being מכף רגלך ועד קדקדך – even these simple facts must have made these theorists pause. Let us consider further: In verses 10, 15, 16 & 17, it repeatedly tells us that the appearance of מחיה, healthy flesh forming on the diseased spot, is a sign of טומאה, while its disappearance and the נגע breaking out in its place renders טהרה again; verse 12 tells us that no careful examination is required in the folds of the body, but only לכל מראה עיני הכהן, only in those parts of the body which are directly visible to the eye of the כהן, in Ch. XIV, 36, the priest is expressly ordered to remove everything out of the house before he makes his examination, as should he have to declare the house טמא, everything in it becomes likewise טמא, and if the purpose of the isolation is to prevent the spread of infection, it would be a very peculiar procedure to take out the suspectedly infected clothes, bedding, utensils, etc., out of consideration for the loss to the owner! Altogether the Halacha learns from this that these “sanitary officers” in priestly garb are to adopt a very conservative attitude in every way and always to give the benefit of every doubt, which in dealing with such a “dangerous”, “horrible” disease as “leprosy” would be perfectly senseless if their טמא declaration and the isolation which it entails were to be for the purpose of prevention of the spread of infection. When would such “police” activity and protective isolation be most demanded but where and when large masses of people gather and the unhindered mixing of the “leper” amongst the crowds would be a real danger of infection to whole families, even to the whole nation! And yet, just on such occasions, the inspection-functions of the priests were completely in abeyance. During the week of wedding gatherings, during the whole of the pilgrim festivals, when the whole nation streamed into Jerusalem, altogether on any Sabbath or Festival, no נגע was examined, (see note on v. 14). Just in Jerusalem, leprosy in houses was not considered of any consequence at all, (see note on CH. XIV, 34). We have already drawn attention (on v. 59) to the rule that כל ספק נגעים בתחלה טהור, which prescribes a more lenient ruling than is generally applied to איסורים of the Torah (where the reverse is the case. I.L.), whereas, if it were dealing with diseases and precautions against contracting them, according to the principle that חמירא סכנתא מאיסורא, (Chulin 10a), the rule would be just for נגעים to impose a stricter, more rigorous practice. We have seen above that even in a case where there is absolute certainty of the existence of a symptom showing the נגע to have character of טומאה, if there is any doubt to which of two נגע spots on the same person the symptom applies, the טומאה declaration is not to be made! Further, as quoted on v. 46, it is only out of such cities which were surrounded by a wall at the time the Land was taken into possession, even if they had lost these walls later on, that a מצורע had to be expelled! Throughout the whole open country and in open towns, or even in towns which had been enclosed by walls later on, the מצורע was allowed to move freely among the people, and no quarantine was imposed to protect the people from this alleged infection of leprosy; only leprosy in clothes, had to be expelled from all towns or inhabited places everywhere! Consider also that all these laws only apply to the Jewish inhabitants of Israel. No non-Jew became טמא by any נגע, his נגע was not examined, no expulsion or isolation was imposed on him, and even if he became a Jew, no נגע which he had contracted before his conversion was of any consequence (see on v. 2). Equally so, none of these laws apply to the appearance of any leprosy on the clothes or house of a non-Jew while these were in his possession (see on v. 47).

These, and similar considerations make it quite impossible to think that this chapter deals with sanitary or prophylactic measures against disease, or that we have to regard our כהנים – regarding whom, in any case, no trace of any reference to remedial measures can be found in the whole chapter – as functioning in the health or medical care of the people.

And, as a matter of fact, the symptoms described in our chapter have nothing at all in common with the diseases which are described in books of medical science on skin diseases under the heading of “Lepra”, leprosy. Whereas these, all start with an inflammatory swelling which makes the skin darker in colour, our נגעים consist solely of white patches, of greater or lesser bleaching of the skin, at which ת”כ expressly says there is no swelling or raising of the skin. Zipporno – who was a doctor, – in his commentary on the Torah remarks on the complete difference between these נגעים and the dreadful diseases which he found described under the name of leprosy in scientific medical writings. We had, accordingly, long been completely convinced that the sequestration and expulsion which the Torah prescribes for a מצורע is in no way meant to be a protection against any possible infection, when we read in the journal “Ausland” No. 14, 1868, that a commission had been appointed by the British Government to investigate the terrible increase in the number of cases of the quite common occurrence of leprosy in the colonies, and their report was reproduced in that Journal. The “Report on Leprosy by the Royal College of Physicians” stated that the investigation resulted in the finding that leprosy even in its most terrible form is not at all infectious. “The all-important question for the Government” the report continues, “is whether this disease is contagious or not. There can be no doubt that the Jews considered it to be so, and that the strictest quarantine was imposed upon those who contracted it. Nevertheless, it seems probable from several indications that the Jews of old classified all skin diseases as leprous, and accordingly people who were affected by the contagious disease of modern Europe, such as measels, scarlet fever or smallpox, were included in the laws of quarantine for leprosy. It is a remarkable fact, moreover, that present-day Jews seem to be less liable to the attacks of contagious illnesses than their European neighbours, which may be due to a trace which still remains from those ceremonious practices which exercised such great influence on the physical forces and energies of the ancient Jews. Be that as it may, the practically unanimous conviction of our investigating reporters from all parts of the world is: the disease is not infectious“.

We have seen that the widespread view that the biblical injunctions regarding sequestration are regulations to prevent infection rests entirely on a mistaken premise.

If then the understanding of the Negaim-laws as being sanitary-police regulations must definitely be relegated to the realm of fairy-tales, let us turn to the Torah itself, which in any case, leaves us in no possible doubt whatever as to in which light it wishes these laws to be regarded. In Deut. XXIV,8, in the midst of a list of laws referring entirely to social matters and all dealing with the respect due to human worth and benevolent consideration for the happiness and well-being of others, we come across this warning: השמר בנגע צרעת וגו’‏ , “Take heed in the plague of leprosy that thou observe diligently and do according to all that the priests, the Levites, shall teach you, as I have commanded them so shall ye observe to do. Remember what G-d, your G-d, did unto Miriam on the way when ye went out of Egypt”. By this, the meticulous observation of the laws given in our chapter here is made the conscientious duty of every single individual. From the term השמר is specially derived the prohibition of removal of the נגע by surgical or other means, although, or rather because, מן התורה thereby all טומאה and isolation ceases, (see v. 46, a fact which incidentally again excludes any precautionary health motives for the sequestration. For, if this were the case, the removal of the נגע would be most desirable as we are told that the necessity for sequestration ceases thereby) as well as the demand for the exact carrying out of all the positive commands given here. Both, the negative command, the prohibition, and the positive demand, are then supported by a reference to a certain incident in the life of Miriam, the Prophetess, which incident is to remain forever in national remembrance. This remembrance clearly refers to the incident recorded in Numb. XII. Miriam had spoken slander about Moses, and following this לשון הרע had become “leprous” and had been expelled from the camp for seven days, and there this leprosy and this expulsion had been explained as being a sign of, and for her to take to heart, G-d’s displeasure at her behaviour. “If her father”, so runs G-d’s reply to Moses’s prayer that his sister should be cured, “if her father had so spat out before her, would she not remain ashamed for seven days? Let her be secluded outside the camp for seven days, thereafter let her be received again”. ואביה ירק ירק בפניה, a sign of disgust, as a sign of a father’s displeasure mounting to contempt, G-d say, the צרעת he sends is to be taken. Now, this punishing stroke was sent as a result of a social sin, a sin, which, is is there shown, consisted of both slander and over-rating oneself, presumption, conceit. If then every נגע צרעת in the future that shows itself on any member of the Jewish Nation is to recall this experience of Miriam, every such נגע צרעת is to be taken as a punitive admonition for social misbehaviour; and the expulsions מחוץ למחנה, out of the national circle which has the Sanctuary of the Torah as its centre, has, – as it says with Miriam – no other purpose or reason than הכלם, than to let oneself be permeated with the consciousness of one’s complete unworthiness – (Whereas בוש means finding oneself deceived regarding something one had expected in the future, one’s expectations, החפיר regarding a misunderstood past, הכלם is the feeling brought about by becoming conscious of present loss of worthiness). The expulsion tells the מנוגע, the one who is affected by צרעת, literally the one who is touched (נגוע. I.L.), by the Finger of G-d, that he has forfeited the merit of remaining in the social circle of G-d’s Sanctuary.

And actually we find that the teaching of our חכמים always takes “Negaim” as being a punishment sent by G-d, primarily for sins of the tongue, לשון הרע, but then generally for the cardinal sins of social life, of which they enumerate seven. It says in Berachoth, 5b: כל מי שיש בו אחד מארבעה מראות נגעים הללו אינן אלא מזבח כפרה, “Being affected by one of these four appearances is nothing other than an altar for atonement”. And in Arachin 16b: מה נשתנה מצורע שאמרה תורה בדד ישב מחוץ למחנה מושבו הוא הבדיל בין איש לאשתו בין איש לרעהו לפיכך אמרה תורה בדד ישב וגו’‏ , “Why just for the מצורע is it ordained, ‘he shall dwell apart, outside the camp is his dwelling to be’? He caused separation between man and wife, between friend and friend, therefore is he, too, to be separated from everybody, let him remain alone, outside the camp”; מה נשתנה מצורע שאמרה תורה יביא שתי צפרים לטהרתו, אמר הקב”ה, הוא עשה מעשה פטיט, לפיכך יביא קרבן פטיט, “Why just for the מצורע is it ordained that in his offering to regain טהרה he is to represent his personality by two birds? He sinned by chattering, therefore is he to bring a twittering offering”. Similarly in ויקרא רבה: א”ר יהושע בן לוי, חמש תורות כתובות במצורע: זאת תורת נגע צרעת וגו’, זאת תהיה תורת “המצורע”, תורת “המוציא רע”, ללמדך שכל האומר לשון הרע עובר על חמשה חומשי תורה, where the play is made on the word מצורע as, phonetically, being able to be split up into מוציא רע, to give its meaning as slanderer. So also in Arachin 15b: זאת תהיה תורת המצורע, זאת תהיה תורתו של מוציא שם רע. Elsewhere, in Arachin 16a, seven social sins and bad habits are reckoned as a consequence of which Negaim are sent: על שבעה דברים נגעים באין על לשון הרע ועל שפיכת דמים ועל שבועת שוא ועל גלוי עריות ועל גסות הרוח ועל הגזל ועל צרות העין, as a result of the sins of slander, of spilling of blood, of perjury, of sexual immorality, of pride, of robbery and of unkind selfishness. In ויקרא רבה on פ’ מצורע, the following are reckoned: – עינים רמות, לשון שקר, וידים שופכות דם נקי, לב חורש מחשבות און, רגלים ממהרות לרוץ לרעה, יפיח כזבים, עד שקר and משלח מדנים בין אחים; a lying tongue, proud eyes, hands spilling innocent blood, a heart pondering on thoughts of violence, feet always ready to run for evil purposes, spreading lies about, and bringing about quarrels between brothers and giving false witness. These are the six and seven things which are described in Prov. VI,16 as being hated by G-d, and abominated by His Holy Nature: שש הנה שנא ד’ ושבע תועבות נפשו. And the division into six and seven is explained: שביעית קשה כנגד כולן ואי זה, זה משלח מדנים, that the seventh, bringing and causing discord, (i.e. לשון הרע), is designated as the one which is worse than all the others put together. And, as a matter of fact, spreading slander, which does bring about the spiritual death of respect and love between even brothers and sisters, does combine in its consequences all the other imperfections and sins. And inasmuch as these imperfections and sins are not mentioned in the abstract but referred to the various organs of the body which are misused in practising them, it does not say רום עינים etc., but עינים רמות etc., it is the eye, the mouth, the hand, the heart, the foot; in short, the whole person who, instead of using organs which are given to him for obtaining and practising modesty, truth, doing good, justice, spreading kindness, truth and peace, has made himself the bearer and spreader of the very opposite of all these and has shown himself as the object of hate and abomination of G-d, Who, accordingly, sends him the mark of His deep displeasure and thereby dismisses him from the social purlieus of the Sanctuary of His Torah until הכלם, until he comes to a sense of true self-judgment. When we are told of Miriam, that: ויחר אף ד’ בם וילך והענן סר מעל האהל והנה מרים מצורעת כשלג, everybody is told, everybody on whose self, on whose clothing or house, a נגע appears, that this נגע is a sign that his social behaviour has invoked G-d’s deepest displeasure and that G-d’s protecting and blessing-giving Presence no longer allows him to find a place in His circle.2

Rav Hirsch and Artscroll are, of course, entitled to their opinions; their arguments must certainly be addressed; and as they note, they are, after all, following a well known stance of Hazal, but the authoritative dismissal as “absolute folly” of the attempt to “give [the laws of צרעת] any sanitary character”, and the condescending “relegat[ion] to the realm of fairy-tales” of “the understanding of the Negaim-laws as being sanitary-police regulations” betrays a lack of either erudition or frankness, as this is actually the view of ויקרא רבה, Ramban (in no less than three distinct places in his Biblical commentary), and a number of the Tosafists!

ויקרא רבה

רבי יוחנן ור’ שמעון בן לקיש ר’ יוחנן אומר: אסור לילך במזרחו של מצורע ארבע אמות.
ור’ שמעון אמר: אפילו מאה אמה.
ולא פליגי, מאן דאמר ד’ אמות בשעה שאין הרוח יוצא.
ומאן דאמר ק’ אמה בשעה שהרוח יוצא.
רבי מאיר, לא אכיל ביעי מן מבואה דמצורע.
ר’ אמי ור’ אסי, לא הוו עיילי למבואות של מצורע.
ריש לקיש, כד הוה חמי חד מנהון במדינתא, מרגם להון באבניא.
אמר לו: פוק לאתרך לא תזהום ברייתא.
דתני ר’ חייא (ויקרא יג) בדד ישב לבדו.
ישב ר’ אלעזר ברבי שמעון, כד חמי חד מנהון, הוה מיטמר מיניה, על שום דכתיב: זאת תהיה תורת המצורע, המוציא שם רע:3

רבי יוסף בכור שור

בדד ישב. שזה החולי מתפשט על בני אדם הרגילים אצלו, ולכך יהיה בדד שלא ירגיל אדם אליו ואסור בתשמיש המטה שהתשמיש ממקמקו.

מחוץ למחנה. וגם זה מפני שלא יתקרב אצל בני אדם מפני החולי גם מפני הטומאה, שהוא מטמא בביאה כמת.4

רמב”ן

ועוד בו ענין [באיסור ההבטה לאחוריהם ללוט ומשפחתו בבריחתם מסדום], כי הראות באויר הדבר ובכל החליים הנדבקים, יזיק מאד וידביקם, וכן המחשבה בהם, ולכן יסגר האיש המצורע וישב בדד (ויקרא יג מו). וכן נשוכי חיות השוטות ככלב השוטה וזולתו, כאשר יראו המים וכל מראה יחזו בהם דמות המזיק וישתטו וימותו, כמו שאמרו במסכת יומא (פד א), והזכירוהו אנשי הטבע. ולכן הייתה אשתו של לוט נציב מלח, כי באתה המכה במחשבתה כאשר ראתה גפרית ומלח היורד עליהן מן השמים ודבקה בה:5

Additionally, the sixteenth-century rabbi and medical student R. Avraham Menahem Rapoport even suggests that at least one of the reasons for the Biblical injunction that the מצורע “shall put a covering upon his upper lip” is to shield others from the contamination of his breath:

ועל שפם יעטה. כדי שלא ידבר עוד לשון הרע כמקדם. ושלא יטמא אחרים בהבל פיו. וכן טמא טמא יקרא כדי שיתרחקו ממנו הבריות: …

בדד ישב. כי ריחו והבלו מזיקים. נכנס לבית הכנסת עושים לו מחיצה רחבה ד’ על ד’ אמות וגבוה ב’ נכנס ראשון ויוצא ראשון. וגם שאר מצורעים אינם יכולים להתחבר עמו כי אין כל הצרעיות שוים:6

Regarding Rav Hirsch’s assertion, in reliance on the “Report on Leprosy by the Royal College of Physicians”, that leprosy is not infectious, and that “the widespread view that the biblical injunctions regarding sequestration are regulations to prevent infection” therefore “rests entirely on a mistaken premise”: it is actually Rav Hirsch and the British investigators who are mistaken; to the best of modern scientific knowledge, leprosy is contagious, although the level of contagion is not nearly as severe as was once believed:

Leprosy, also known as Hansen’s disease (HD), is a chronic infection caused by the bacteria Mycobacterium leprae and Mycobacterium lepromatosis. …

Although the mode of transmission of leprosy remains uncertain, many think that M. leprae is usually spread from person to person in nasal droplets. Studies have shown that leprosy can be transmitted to humans by armadillos. Leprosy is not known to be either sexually transmitted or highly infectious after treatment. Approximately 95% of people are naturally immune and sufferers are no longer infectious after as little as two weeks of treatment.

The mechanism of transmission of leprosy is prolonged close contact and transmission by nasal droplet. In addition to humans, leprosy has been observed in the nine-banded armadillo, (which, it has recently been confirmed, are among the primary sources of new cases of leprosy in Americans), and three species of primates. The bacterium can also be grown in the laboratory by injection into the footpads of mice. There is evidence that not all people who are infected with M. leprae develop leprosy, and genetic factors have long been thought to play a role, due to the observation of clustering of leprosy around certain families, and the failure to understand why certain individuals develop lepromatous leprosy while others develop other types of leprosy. It is estimated that due to genetic factors, only 5% of the population is susceptible to leprosy. This is mostly because the body is naturally immune to the bacteria, and those persons that do become infected experience severe allergic reactions to the disease. However, the role of genetic factors is not entirely clear in determining this clinical expression. In addition, malnutrition and prolonged exposure to infected persons may play a role in development of the overt disease.

The most widely held belief is that the disease is transmitted by contact between infected persons and healthy persons. In general, closeness of contact is related to the dose of infection, which in turn is related to the occurrence of disease. Of the various situations that promote close contact, contact within the household is the only one that is easily identified, although the incidence among contacts and the relative risk for them appear to vary considerably in different studies. In incidence studies, infection rates for contacts of lepromatous leprosy have varied from 6.2 per 1000 per year in Cebu, Philippines to 53 per 1000 per year in part of Western India to 55.8 per 1000 per year in a part of Southern India. …7

Remarkably:

The causative agent of leprosy, Mycobacterium leprae, was discovered by G. H. Armauer Hansen in Norway in 1873, making it the first bacterium to be identified as causing disease in humans.8

I recently made a study of the tension in our tradition between the theological view of disease as punishment for sin, and the naturalistic one that assumes physical cause and effect; the focus was a survey of Halachic perspectives on the propriety and religious legitimacy of prudent precautions to avoid contagion. An audio lecture, a couple of versions of an article, and my notes are available, as always, from the Internet Archive.

Further reading:

  1. The Chumash – The Stone Edition (ArtScroll / Mesorah), Vayikra / Leviticus introduction to Chapter 13, pp. 609-10. []
  2. The Pentateuch, Translated & Explained by Samson Raphael Hirsch, Vol. III Leviticus (part I), rendered into English by Isaac Levy (London 1958), pp. 355-60. []
  3. ויקרא רבה מצורע פרשה ט”ז אות ג’ – קשר.‏ []
  4. פירושי רבי יוסף בכור שור על התורה (מוסד הרב קוק) ויקרא יג:מו עמוד קצט, הובא בקיצור בחזקוני (קשר) ובהדר זקנים (קשר) שם.‏ []
  5. פירוש הרמב”ן על התורה בראשית (וירא) יט:יז – קשר.‏ []
  6. מנחה בלולה סוף תזריע – קשר, הובא בחומש אוצר הראשונים שם.‏ []
  7. Wikipedia contributors, “Leprosy,” Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Leprosy&oldid=559879146 (accessed June 18, 2013). []
  8. Wikipedia contributors, “History of leprosy,” Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=History_of_leprosy&oldid=559777802 (accessed June 18, 2013). []