Leviticus 13:1-3

The LORD said to Moses and Aaron, “If anyone has a swelling or a rash or discolored skin that might develop into a serious skin disease, that person must be brought to Aaron the priest or to one of his sons. The priest will examine the affected area of the skin. If the hair in the affected area has turned white and the problem appears to be more than skin-deep, it is a serious skin disease, and the priest who examines it must pronounce the person ceremonially unclean.