Leviticus 13:34-37

13:34 The priest must then examine the scall on the seventh day, and if the scall has not spread on the skin and it does not appear to be deeper than the skin, then the priest is to pronounce him clean. So he is to wash his clothes and be clean. 13:35 If, however, the scall spreads further on the skin after his purification, 13:36 then the priest is to examine it, and if the scall has spread on the skin the priest is not to search further for reddish yellow hair. The person is unclean. 13:37 If, as far as the priest can see, the scall has stayed the same and black hair has sprouted in it, the scall has been healed; the person is clean. So the priest is to pronounce him clean.