As Ahab had imported Baal worship from Phoenicia, so Ahaz imported a foreign altar from Damascus (cf. Jehoash's Edomite idols; 2 Chron. 25:14, 20). As Judah's king-priest, he led the nation in worshipping at an altar different from what Yahweh had specified (Exod. 27:1-8). Furthermore he removed the altar God had established from the place God had said it should occupy in the temple courtyard (Exod. 40:6, 29).
"Readers could hardly miss the similarities between Jeroboam, the father of institutionalized idolatry in Israel, and Ahaz, the Judahite king who makes polytheism acceptable nationwide."105
He did not completely discard the worship God had prescribed, but he changed it according to his liking thus claiming God's authority (v. 15). The high priest unfortunately cooperated with the king. Ahaz likewise changed the other temple furnishings to please the Assyrian king (v. 18).106