Leviticus 13:22

And if it spread much abroad in the skin
Upon viewing it on the seventh day, though it is not expressed, the swelling or bright spot; or "in spreading spread"; (See Gill on Leviticus 13:7); which Ben Gersom interprets, not of the skin of the flesh, but of the ulcer: then the priest shall pronounce him unclean;
even though there are no white hairs in it, nor is it lower than the skin, yet is not at a stand or contracted, but spreading: it [is] a plague;
or stroke; it is one sort of a leprosy, and such an one as makes a man unclean in a ceremonial sense.