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.

And if it spread much abroad in the skin, then the priest shall pronounce him unclean: it is a plague.

13:22 A plague - Or the plague of leprosy, of which he is speaking.

13:18-44 The priest is told what judgment to make, if there were any appearance of a leprosy in old sores; and such is the danger of those who having escaped the pollutions of the world are again entangled therein. Or, in a burn by accident, ver. 24. The burning of strife and contention often occasions the rising and breaking out of that corruption, which proves that men are unclean. Human life lies exposed to many grievances. With what troops of diseases are we beset on every side; and thy all entered by sin! If the constitution be healthy, and the body lively and easy, we are bound to glorify God with our bodies. Particular note was taken of the leprosy, if in the head. If the leprosy of sin has seized the head; if the judgment be corrupted, and wicked principles, which support wicked practices, are embraced, it is utter uncleanness, from which few are cleansed. Soundness in the faith keeps leprosy from the head.