C. F. Keil and Franz Delitzsch on Leviticus 13:42-44

Lev 13:42-44

But if a white reddish mole was formed upon the bald place before or behind, it was leprosy breaking out upon it, and was to be recognised by the fact that the rising of the mole had the appearance of leprosy on the skin of the body. In that case the person was unclean, and to be pronounced so by the priest. “On his head is his plague of leprosy,” i.e., he has it in his head.