Leviticus 13:5-9

Then the priest shall look at him on the seventh day, and if in his eyes the infection has not changed and the infection has not spread on the skin, then the priest shall isolate him for seven more days.

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.