Midrash su Levitico 14:44

1) (Vayikra 14:43) ("And if the plague-spot returns and blossoms in the house after he removed the stones and after the house has been scraped and after it has been plastered. (Vayikra 14:44) And the Cohein shall come and he shall see, and, behold, the plague-spot has spread in the house, it is blight leprosy in the house; it is tamei.") "And if the plague-spot returns and blossoms in the house": Just as we speak of a man returning to his place, here, too, the plague-spot returns to the same stones. This tells me only of his place. Whence do we derive the entire house for inclusion? From "in the house." I might think that the size of a garis (makes it subject to tumah); it is, therefore, written here "plague-spot" and before, (Vayikra 14:37), "plague-spot." Just as there, two garisin, here, too, two garisin.

5) Now if we are stringent with garments, where if the plague-spot remains the same at the end of two weeks, the garment is burned, should we be stringent with houses, where if the plague-spot remains the same after two weeks the house is not razed! It is, therefore, written "blight leprosy" (here) - "blight leprosy" (Vayikra 13:5), in respect to garments) for an identity (gezeirah shavah). Just as with garments, a returning plague-spot confers tumah even without spreading, so with houses, a returning plague-spot confers tumah even without spreading.

7) And whence is it derived that if it remained as it was at the end of the first week and it spread in the second week, he removes and scrapes and plasters, and he is given another week? From (Vayikra 13:44) "And the Cohein shall come and see, and, behold, the plague-spot has spread." Of what is this speaking? If of spreading in the first week, this has already been stated. It must be speaking, then, of his having come at the end of the first week and finding it to have remained the same, and coming at the end of the second week and finding it to have spread. What should be done? I derive it inductively from the spreading of the first week, i.e., he removes, scrapes, and plasters, and is given an additional week. The same obtains with the spreading of the second week. — Now if we were lenient with spreading in the first week, it is because we were lenient with its remaining the same. Shall we then be lenient with spreading in the second week, where we are stringent with its remaining the same? It is, therefore, written (re the end of the first week, Vayikra 13:39) "And the Cohein shall return," and (re the end of the second week, Vayikra 13:44) "And the Cohein shall come." Returning and coming are one and the same. Just as with "returning," he removes, scrapes, and plasters, and is given an additional week, so, with "coming."