John Wesley on Leviticus 13:6

Dark - Contrary to the white colour of the leprosy. But the word may be rendered, have contracted itself, and thus the opposition seems to be most clear as the spreading of itself. He shall wash his clothes - Though it was no leprosy, to teach us, that no sin is so small as not to need to be washed by the blood of Christ, which was the thing designed by all these washings.