Charles Ellicott Commentary Leviticus 13:6

"and the priest shall look on him again the seventh day; and, behold, if the plague be dim, and the plague be not spread in the skin, then the priest shall pronounce him clean: it is a scab: and he shall wash his clothes, and be clean." — Leviticus 13:6 (ASV)

And the priest shall look on him again. —If, on further examination at the end of another week, the priest finds that the bright spot looks darker and has not spread, he is to pronounce the patient clean and release him, since it was simply an ordinary scurf. However, though not leprous, the eruption indicated some impurity in his blood, and he therefore had to wash his garments.