Leviticus 13:30-31
30 the priest is to examine the sore, and if it appears to be more than skin deep and the hair in it is yellow and thin, the priest shall pronounce that person unclean; it is an itch, an infectious disease of the head or chin.
31 But if, when the priest examines this kind of sore, it does not seem to be more than skin deep and there is no black hair in it, then the priest is to put the infected person in isolation for seven days.