Leviticus 13:6-10

The 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 wash his clothes and be clean.

“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.

And the priest shall look, and if the rash has spread on the skin, then the priest shall pronounce him unclean; it is leprosy.

“When the infection of leprosy is on someone, then he shall be brought to the priest.

The priest shall then look, and if there is a white swelling on the skin, and it has turned the hair white, and there is new raw flesh in the swelling,