Leviticus 13:20-23

²⁰And if, when the priest seeth it, behold, it be in sight lower than the skin, and the hair thereof be turned white; the priest shall pronounce him unclean: it is a plague of leprosy broken out of the boil.

²¹But if the priest look on it, and, behold, there be no white hairs therein, and if it be not lower than the skin, but be somewhat dark; then the priest shall shut him up seven days:

²²And if it spread much abroad in the skin, then the priest shall pronounce him unclean: it is a plague.

²³But if the bright spot stay in his place, and spread not, it is a burning boil; and the priest shall pronounce him clean.