My lecture (available at the Internet Archive) and weekly column for these past פרשיות תזריע ומצורע discussed the Talmudic principles of מאי דהוה הוה and דרוש וקבל זכר, and the practical applicability of the laws of נגעי בתים in particular:
Parashiyos Tazria and Metzora contain the detailed laws of several forms of tzaraas (commonly, but not necessarily accurately, translated as ‘leprosy’): afflictions of the skin, the hair of the head or beard, garments, warp and woof, and leather, and houses.
As we have discussed elsewhere, there is considerable debate over whether the tzaraas of the body referred to by the Torah is a natural, contagious disease, or a supernatural ailment. With regard to tzaraas of garments and houses, the Rambam declares that “they are not of the way of the world, but were a sign and wonder in Israel to warn them against evil speech” (Tumas Tzaraas 16:10).
With regard to tzaraas of houses in particular, there are conflicting views in the Talmud over the practical applicability of the relevant laws. One opinion maintains that due to the extremely specific conditions that must be met for a house to be deemed afflicted with tzaraas, “[I]t never was and it never will be, so why was it written [in the Torah]? Investigate [the laws] and receive reward!” But the Talmud then proceeds to cite a couple of sages who assert the existence of actual, specific sites where an afflicted house had been demolished and where the stones removed from an afflicted house had been deposited (Sanhedrin 71a). Furthermore, Rashi on parashas Metzora (14:34) cites a midrash that apparently interprets the Torah’s introductory language to the laws of tzaraas on houses “and I will place a tzaraas affliction” as an assurance that such afflictions will indeed occur. The midrash goes on to explain, however, that this is actually good news: “for the Emorites had hidden caches of gold in the walls of their houses all forty years that the Jews were in the desert, and via the affliction [the Jewish homeowner] demolishes the house and finds them”.
See also our previous discussion of the Talmudic assertions that certain scenarios described in the halachic portions of the Torah “never were and never will be”.