Leviticus 13:2-6

“When a person has on the skin of his body a swelling or an eruption or a spot, and it turns into a case of leprous disease on the skin of his body, then he shall be brought to Aaron the priest or to one of his sons the priests, and the priest shall examine the diseased area on the skin of his body. And if the hair in the diseased area has turned white and the disease appears to be deeper than the skin of his body, it is a case of leprous disease. When the priest has examined him, he shall pronounce him unclean. But if the spot is white in the skin of his body and appears no deeper than the skin, and the hair in it has not turned white, the priest shall shut up the diseased person for seven days. And the priest shall examine him on the seventh day, and if in his eyes the disease is checked and the disease has not spread in the skin, then the priest shall shut him up for another seven days. And the priest shall examine him again on the seventh day, and if the diseased area has faded and the disease has not spread in the skin, then the priest shall pronounce him clean; it is only an eruption. And he shall wash his clothes and be clean.