Therefore — To chastise your pride, and defeat your hopes. Set up — The Assyrians, who, presently after this prophecy, prevailed against him, 2 Kings 16:7. He mentions Rezin, because he was confederate with Ephraim. Join — So that they shall invade him from several quarters. His — Not Rezin's, but Ephraim.
Related Commentaries of Isaiah 9:11
Isaiah 9:11
11 Therefore the LORD shall set up the adversaries of Rezin against him, and joinb his enemies together;