Leviticus 13:4-6

But if the mark on his skin is white, and does not seem to go deeper than the skin, and the hair on it is not turned white, then the priest will keep him shut up for seven days; And the priest is to see him on the seventh day; and if, in his opinion, the place on his skin has not become worse and is not increased in size, then the priest will keep him shut up for seven days more: And the priest is to see him again on the seventh day; and if the mark is less bright and is not increased on his skin, then let the priest say that he is clean: it is only a skin-mark, and after his clothing has been washed he will be clean.