Charles Ellicott Commentary Leviticus 13:23

"But if the bright spot stay in its place, and be not spread, it is the scar of the boil; and the priest shall pronounce him clean." — Leviticus 13:23 (ASV)

But if the bright spot stay. —As the spreading of the spot is a sure sign of the disease lurking in the system, its continuing in the same condition showed that it was simply the reopening of the boil. The priest is therefore to pronounce the patient clean, or clear of leprosy.