Leviticus 13:21-23

21But if, when the priest examines it, there is no white hair in it and it is not more than skin deep and has faded, then the priest is to isolate them for seven days. 22If it is spreading in the skin, the priest shall pronounce them unclean; it is a defiling disease.

23But if the spot is unchanged and has not spread, it is only a scar from the boil, and the priest shall pronounce them clean.