Leviticus 13:21-23

21But if the priest finds no white hair on the affected area and the problem appears to be no more than skin-deep and has faded, the priest must quarantine the person for seven days.

22If during that time the affected area spreads on the skin, the priest must pronounce the person ceremonially unclean, because it is a serious disease.

23But if the area grows no larger and does not spread, it is merely the scar from the boil, and the priest will pronounce the person ceremonially clean.