Charles Ellicott Commentary Leviticus 13:43

"Then the priest shall look upon him; and, behold, if the rising of the plague be reddish-white in his bald head, or in his bald forehead, as the appearance of leprosy in the skin of the flesh;" — Leviticus 13:43 (ASV)

Then the priest shall look. —It is then the duty of the priest to ascertain whether the white-reddish rising in the baldness on the back of the head or the bald forehead is in appearance like the leprosy in the skin of the flesh described in Leviticus 13:2, excepting, of course, the white hair, which in this case could not exist.

As the leprosy appeareth in the skin of the flesh. —Better, in appearance like the leprosy in the skin of the flesh. Though the reddish-white eruption is the only symptom mentioned by which head-leprosy is to be recognised, and nothing is said about remanding the patient if the ailment should appear doubtful, as in the other cases of leprosy, yet because it is here said “in appearance like the leprosy in the skin of the flesh,” the administrators of the law during the second Temple inferred that all the criteria specified in one are implied in the other.

They interpret this phrase as, “they are, and therefore must be treated like, leprosy in the skin of the flesh.” Hence they submit that there are two symptoms which render baldness in the front or at the back of the head unclean, namely:

1. Live or sound flesh; and
2. Spreading.

“If live or sound flesh is found in the bright spot on the baldness at the back or in the front of the head, he is pronounced unclean; if there is no live flesh, he is confined, and examined at the end of the week, and if live flesh has developed, and it has spread, he is declared unclean, and if not, he is confined for another week.

If it spreads during this time, or produces live flesh, he is declared unclean, and if not, he is declared clean. He is also pronounced unclean if it spreads or produces sound flesh after he has been declared clean.” Of course, the fact that the ailment in this instance develops on baldness precludes white hair being among the criteria indicating uncleanness.