Leviticus 13:29-33

29If a man or woman has an infection on the head or chin, 30the priest shall examine the infection, and if it appears to be deeper than the skin and the hair in it is yellow and thin, the priest must pronounce him unclean; it is a scaly outbreak, an infectious disease of the head or chin.

31But if the priest examines the scaly infection and it does not appear to be deeper than the skin, and there is no black hair in it, the priest shall isolate the infected person for seven days. 32On the seventh day the priest is to reexamine the infection, and if the scaly outbreak has not spread and there is no yellow hair in it, and it does not appear to be deeper than the skin, 33then the person must shave himself except for the scaly area. Then the priest shall isolate him for another seven days.