John Wesley on 2 Chronicles 26:21

His death - God would have this leprosy to be incurable, as a lasting monument of his anger against such presumptuous invaders of the priest's office. Dwelt, &c. - As he was obliged to do by law, which he durst not now resist, being under the hand of God, and under the fear of worse plagues, if he did not so. For - He dwelt in a several house, because he might not come into the temple or courts, nor consequently into any publick assembly. So the punishment answered the sin, as face does to face in a glass. He thrust himself into the temple of God, whether the priests only had admission: and for that was thrust out of the very courts of the temple, into which the meanest of, his subjects might enter. He invaded the dignity of the priesthood, to which he had no right, and is for that deprived of the royal dignity, to which he had an undoubted right.