Leviticus 13:4-8

If the shiny spot on the skin is white but does not appear to be more than skin deep and the hair in it has not turned white, the priest is to isolate the affected person for seven days. On the seventh day the priest is to examine them, and if he sees that the sore is unchanged and has not spread in the skin, he is to isolate them for another seven days. On the seventh day the priest is to examine them again, and if the sore has faded and has not spread in the skin, the priest shall pronounce them clean; it is only a rash. They must wash their clothes, and they will be clean. But if the rash does spread in their skin after they have shown themselves to the priest to be pronounced clean, they must appear before the priest again. The priest is to examine that person, and if the rash has spread in the skin, he shall pronounce them unclean; it is a defiling skin disease.