Leviticus 13:2-6

“When a man has a swelling on the skin of his body, a scab, or a bright spot, and it becomes the infection of leprosy on the skin of his body, then he shall be brought to Aaron the priest, or to one of his sons the priests. The priest shall look at the diseased spot on the skin of his body, and if the hair in the infection has turned white and the infection appears deeper than the skin of his body, it is an infection of leprosy; when the priest has looked at him, he shall pronounce him [ceremonially] unclean. If the bright spot is white on the skin of his body and does not appear to be deeper than the skin, and the hair on it has not turned white, the priest shall isolate the person who has the infection for seven days. The priest shall examine it on the seventh day, and if in his estimation the infection has not changed and has not spread on the skin, then the priest shall isolate him for seven more days. The priest shall examine him again on the seventh day, and if the infection has a more normal color and the spot has not spread on the skin, the priest shall pronounce him clean; it is only a scab; and he shall wash his clothes and be clean.