Midrash su Levitico 13:10

1) (Vayikra 13:4) ("And if it is a white bahereth in the skin of his flesh, and its appearance is not deeper than the skin, and its hair has not turned white, then the Cohein shall quarantine the plague-spot for seven days.") This tells me only of a white bahereth. Whence do we derive for inclusion a (white) se'eth? From (Vayikra 13:10) "a white se'eth." Whence are other (white) appearances derived? From "And if a bahereth."

1) (Vayikra 13:9) ("A plague-spot of leprosy, if it be in a man, then he shall be brought to the Cohein. (Vayikra 13:10) And the Cohein shall see, and, behold, a white se'eth in the skin, and it has turned the hair white, and the healthiness (michyah) of living flesh within the se'eth"): "a plague-spot of leprosy": What is the intent of this? From "and, behold, a white se'eth" we learn that a se'eth becomes tamei with a michyah. Whence do we derive the same for the other appearances? (From "a plague-spot of leprosy.") — But does this not follow (even without the verse)? viz.: If we find all of the other appearances to be similar to se'eth vis-à-vis becoming tamei through white hair, let them be similar to se'eth vis-à-vis becoming tamei through michyah. And, furthermore, it follows a fortiori, viz.: If all of the appearances are similar to se'eth to become tamei through white hair, which does not confer tumah in karachath (back of the head) and gabachath (front of the head, viz. Vayikra 13:42-43), how much more so should they be similar to se'eth to become tamei through michyah, which does confer tumah in karachath and gabachath! — No, if all of the other appearances are similar to se'eth to become tamei through white hair, it is because white hair confers tumah in shechin (boils) and michvah (burns). Should they then be similar to se'eth to become tamei through michyah, which does not confer tumah in shechin and michvah! It must, therefore, be written "a plague-spot of leprosy" (to tell us that they do become tamei through michyah. And just as a se'eth is an um (a generator of leprosy), so is a bahereth an um. And whence do we derive the same for the other appearances? From the same a fortiori argument (as above) and from the same answer, viz. (It is derived) from "a plague-spot of leprosy."

1) (Vayikra 13:14) ("And on the day that there appears in it living flesh he shall be unclean.") We are hereby taught about limb tips that are revealed (in the midst of the blossoming, the nega having departed from them) that they are tamei, (their having become like living flesh in a bahereth). I might think (that this obtains with) any amount (of revelation); it is, therefore, written here "living flesh," and above (Vayikra 13:10, in respect to michyah) "living flesh." Just as "healthy flesh" mentioned there must be (at least the size of a lentil), here, too, it must be a lentil. These are the words of R. Yossi. R. Meir says: Is he rendered tamei by reason of michyah? Did (we not learn [viz. Chapter 2:9]) that michyah does not confer tumah through limb tips? Rather, this is "a decree of the King," and tumah is (conferred through) any amount. R. Yossi countered: Is he rendered tamei by reason of limb tips? Is he not tamei even if (the living flesh) returns to its middle? It is written here "living flesh," and there, "living flesh." Just as "living flesh" there is lentil-size, so "living flesh" here is lentil-size.