And the man whose hair is fallen off his head,.... That is, from the back part of his head, from the crown of his head toward his neck behind:
he is bald; in that spot of the head where the hair is fallen off; and it denotes such a baldness as is occasioned by that, for it signifies one that had hair, but it is fallen off; whereas the baldness after spoken of is thought by some to be of such who never had any hair; though others will have it, that this intends a person bald all over; but it seems plain from what follows, that it designs one whose hair was fallen off behind, and was bald on that part only; and it may be observed, that this is only said of a man, not of a woman, because, as Aben Ezra remarks, she has much moisture in her, and therefore her head does not become bald; hair being like to grass, which flourishes in moist places:
yet is he clean; from the leprosy, or from the scalls, as Jarchi observes, because he is not judged by the signs of the head and beard, which are the place of hair, but by the signs of leprosy in the skin of the flesh, i.e. by the raw flesh and spreading.

bald . . . forehead bald--The falling off of the hair, when the baldness commences in the back part of the head, is another symptom which creates a suspicion of leprosy. But it was not of itself a decisive sign unless taken in connection with other tokens, such as a "sore of a reddish white color" [Leviticus 13:43]. The Hebrews as well as other Orientals were accustomed to distinguish between the forehead baldness, which might be natural, and that baldness which might be the consequence of disease.

The leprosy of bald heads. - קרח is a head bald behind; גּבּח, in front, "bald from the side, or edge of his face, i.e., from the forehead and temples." Bald heads of both kinds were naturally clean.