Leviticus 13:32-36

And in the seventh day the priest shall look on the plague: and, behold, if the scall spread not, and there be in it no yellow hair, and the scall be not in sight deeper than the skin;

He shall be shaven, but the scall shall he not shave; and the priest shall shut up him that hath the scall seven days more:

And in the seventh day the priest shall look on the scall: and, behold, if the scall be not spread in the skin, nor be in sight deeper than the skin; then the priest shall pronounce him clean: and he shall wash his clothes, and be clean.

But if the scall spread much in the skin after his cleansing;

Then the priest shall look on him: and, behold, if the scall be spread in the skin, the priest shall not seek for yellow hair; he is unclean.