Leviticus 13:3-8

3The priest shall look at the infected area on the skin of the 1body, and if the hair in the infection has turned white and the infection appears to be deeper than the skin of his 2body, it is an infection of leprosy; when the priest has looked at him, he shall pronounce him unclean. 4But if the bright spot is white on the skin of his 3body, and 4it does not appear to be deeper than the skin, and the hair on it has not turned white, then the priest shall 5isolate the person who has the infection for seven days. 5Then the priest shall look at him on the seventh day, and if in his eyes the infection has 6not changed and the infection has not spread on the skin, then the priest shall 7isolate him for seven more days. 6The priest shall then look at him again on the seventh day, and if the infected area has faded and the infection has not spread on the skin, then the priest shall pronounce him clean; it is only a rash. And he shall 8wash his clothes and be clean.

7“But if the rash spreads farther on the skin after he has shown himself to the priest for his cleansing, he shall appear again to the priest. 8And the priest shall look, and if the rash has spread on the skin, then the priest shall pronounce him unclean; it is leprosy.