Midrash su Levitico 13:29

1) (Vayikra 13:29) ("And a man or a woman — if there be in it a plague-spot, in the head or in the beard (Vayikra 13:30) then the Cohein shall see the plague-spot; and if its appearance is deeper than the skin and there is in it thin yellow hair, then the Cohein shall declare him tamei. It is a nethek (a scall); it is leprosy of the head or the beard.") "And a man": to include a nethek within a nethek (as being tamei). "a man or a woman": This tells me only of a (distinct) man or woman. Whence do I derive for inclusion a tumtum (one whose sex is in doubt) or a hermaphrodite? From "or." "if there be in it a plague-spot in the head or in the beard": This teaches us that the head and the beard do not combine with each other (vis-à-vis the minimum size for tumah).

2) I might think that though they do not combine with each other, they can spread from one to the other (vis-à-vis "spreading" uncleanliness); it is, therefore, written (Vayikra 13:30) "leprosy of the head or the beard" — Just as they do not combine with each other, so they do not spread from one to the other.

3) This tells me (of his being tamei) when he has (a plague-spot) in (both) his head and his beard. Whence do I derive (that he is also tamei) when he has (a plague-spot) in his head, but not in his beard or in his beard and not in his head? From "And a man or a woman — if there be in it a plague-spot, in the head or in the beard."