Leviticus 13:21-23

21But when the priest examines it, if there is no white hair in it, and it is not beneath the skin but is faded, the priest will quarantine him seven days.

22If it spreads further on the skin, the priest must pronounce him unclean; it is in fact a disease.

23But if the spot remains where it is and does not spread, it is only the scar from the boil. The priest is to pronounce him clean.