Charles Ellicott Commentary Leviticus 13:37

"But if in his eyes the scall be at a stay, and black hair be grown up therein; the scall is healed, he is clean: and the priest shall pronounce him clean." — Leviticus 13:37 (ASV)

But if the scall be in his sight at a stay. —Better, But if the appearance of the scall has remained the same.

And that there is black hair grown up therein. —Better, And if black hair has, etc. If, in addition to its not spreading, the healthy colour of the hair has returned, it shows that the patient is cured of the leprosy, and the priest shall pronounce him clean. (See Leviticus 13:31.) According to the administrators of the law, there had to be at least two black hairs, of such a length that the top could bow towards the root. If two hairs grew up on the healed scall, one black and the other white or yellow, or one long and the other short, the patient could not be declared clean.