Leviticus 13:6-8

6The priest shall look at him again on the seventh day, and if the infection has faded and the mark has not spread on the skin, then the priest shall pronounce him clean; it is only a scab. And he shall 1wash his clothes and be clean.

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