To wit, a sacrifice, and that not unto God, but unto the Syrian idols, as appears from 2 Chronicles 28:23,24, to whom that altar was appropriated. Whether he offered by himself, or by a priest, is not certain.
Related Commentaries of 2 Kings 16:12
2 Kings 16:12
12 And when the king was come from Damascus, the king saw the altar: and the king approached to the altar, and offered thereon.