They took their stand against King Uzziah and said, “Uzziah, you have no right to offer incense to the LORD. Only the priests, the descendants of Aaron, are consecrated to burn incense. Leave the sanctuary, for you have acted unfaithfully; you will not receive honor from the LORD God.”
Here is the only blot we find on the name of king Uzziah, and it is such a one as lies not on any other of the kings. Whoredom, murder, oppression, persecution, and especially idolatry, gave characters to the bad kings and some of them blemishes to the good ones, David himself not excepted, witness the matter of Uriah.
Commenting on 2 Chronicles 26:16-23
And Azariah the chief priest, and all the priests, looked upon him, and, behold, he was leprous in his forehead,.... He was leprous all over his body, no doubt, but it appeared in his forehead very remarkably, and was seen by them all, who, without doubt, informed him of his case, and of which he soon became sensible: and they thrust him out from thence...
And they withstood Uzziah the king, and said unto him, [It appertaineth] not unto thee, Uzziah, to burn incense unto the LORD, but to the priests the sons of Aaron, that are consecrated to burn incense: go out of the sanctuary; for thou hast trespassed; neither [shall it be] for thine honour from the LORD God.