Leviticus 13:2-5

2“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.

3The 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.

4If 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.

5The 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.