2 Kings 16:14
And he brought also the brasen altar, which was before the LORD, from the forefront of the house, from between the altar and the house of the LORD, and put it on the north side of the altar. And he brought also the brasen altar, which was before the LORD, from the forefront of the house, from between the altar and the house of the LORD, and put it on the north side of the altar.
2 Kings 16:14 belongs to 2 Kings 15-16, the history of the kings of Israel and Judah including Ahaz of Judah, within 2 Kings 7-23 covering nearly 300 years from Joram of Israel to Hoshea when Israel was ended by Assyria and carried into captivity, with the contemporary kings of Judah running from Ahaziah to Jehoahaz.
While in Damascus Ahaz saw an altar that pleased him and sent its pattern to Urijah the priest with orders to duplicate it, and Urijah obeyed and built it, and on his return Ahaz offered sacrifices upon the new altar. He then moved the brazen altar appointed under David, which was before the Lord between the altar place and the house of the Lord, to an obscure place on the north side of the new altar to make room for the Damascus altar. In the same rearrangement of the temple furniture he removed a Sabbath booth and sent it to the king of Assyria.
The background is that Ahaz acknowledged Tiglath-pileser king of Assyria as his sovereign and paid him tribute, in connection with Tiglath-pileser's overthrow of Damascus in 740 B.C. The inscriptions of Tiglath-pileser list Ahaz of Judah among those who acknowledged his sovereignty and paid tribute, confirming the Bible record.
The act robbed the temple of its treasures and defiled its holy precincts. It was part of paganizing the religion of Judah and corrupting the temple service. It led soon after to closing the great doors of the temple, leaving the lamps unlighted with no incense offered, neglecting the temple, and erecting high places in all the cities of Judah for burning incense to false gods.
Making the Damascus altar was sinful because Ahaz made it for worship, showing that an image or object becomes idolatrous when it is used as an object of worship. The verse applies to God's people looking upon worldly plans and copying them into God's work, following custom and what has gone before and duplicating extravagant methods and expense from older institution to younger without due thought. Seeking and doing the world's work leads to copying worldly methods and taking in a worldly spirit, marring God's work and awakening enmity with worldly concerns with whom they come in competition.