To wit, by God; for God alone did heal or cleanse him really, the priest only ministerially and declaratively, as ministers are said to remit sins, though it be granted that none can truly and properly forgive sins but God, Mark 2:7.
Related Commentaries of Leviticus 14:3
Leviticus 14:3
3 And the priest shall go forth out of the camp; and the priest shall look, and, behold, if the plague of leprosy be healed in the leper;