Leviticus 13:1-3

And the LORD spoke to Moses and Aaron, saying: “When a man has on the skin of his body a swelling, a scab, or a bright spot, and it becomes on the skin of his body like a leprous sore, then he shall be brought to Aaron the priest or to one of his sons the priests. The priest shall examine the sore on the skin of the body; and if the hair on the sore has turned white, and the sore appears to be deeper than the skin of his body, it is a leprous sore. Then the priest shall examine him, and pronounce him unclean.