Jamieson, Fausset and Brown on Isaiah 36:7

7. The Assyrian mistakes Hezekiah's religious reforms whereby he took away the high places (2Ki 18:4) as directed against Jehovah. Some of the high places may have been dedicated to Jehovah, but worshipped under the form of an image in violation of the second commandment: the "brazen serpent," also (broken in pieces by Hezekiah, and called Nehushtan, "a piece of brass," because it was worshipped by Israel) was originally set up by God's command. Hence the Assyrian's allegation has a specious color: you cannot look for help from Jehovah, for your king has "taken away His altars."

to Jerusalem--(De 12:5, 11; Joh 4:20).