But the Lord will set up the adversaries of Rezin against him. The Israelites having been proud of their alliance with the king of Syria, and hoping that everything would succeed to their wish, Isaiah threatens a new change which will take away all their hope and utterly frustrate their designs, for the Assyrians afterwards took arms and waged war with the Syrians. Accordingly, when Rezin had been slain, (2 Kings 16:9,) that country was entirely ruined. Still more does he heighten this, by adding, he shall mingle; [1] for he means that the Lord will gather together and mingle various enemies whom he will commission to destroy the king of Syria, as the soldiers who composed the army of that vast monarchy were collected out of various nations.

Footnotes

1 - And join his enemies together. Margin, Heb. mingle. -- Eng. Ver. -- Calvin, in his version placed at the beginning of this Chapter, renders the clause, and will join his enemies together; but when he comes to explain it, he translates the Hebrew word literally, he will mingle. In both renderings the exact coincidence with our ordinary version deserves notice. -- Ed.

Therefore - This verse indicates the punishment that would come upon them for their pride.
The Lord shall set up - Hebrew, 'Shall exalt.' That is, they shall overcome and subdue him.
The adversaries of Rezin - King of Syria, Isaiah 7:1. It should be observed here, that twenty-one manuscripts, instead of adversaries, read princes of Rezin. The sense seems to require this; as in the following verse, it is said that the Syrians will be excited against them.
Against him - Against Ephraim.
And join his enemies together - Hebrew, 'Mingle them together.' They shall be excited into wild and agitated commotion, and shall pour down together on the land and devour it. In what way this would be done is specified in Isaiah 9:12.

The adversaries of Rezin against him "The princes of Retsin against him" - For צרי tsarey, enemies, Houbigant, by conjecture, reads שרי sarey, princes; which is confirmed by thirty of Kennicott's and De Rossi's MSS., (two ancient), one of my own, ancient; and nine more have צ tsaddi, upon a rasure, and therefore had probably at first שרי sarey. The princes of Retsin, the late ally of Israel, that is, the Syrians, expressly named in the next verse, shall now be excited against Israel.
The Septuagint in this place give us another variation; for רצין Retsin, they read הר ציון har tsiyon, ορος Σιων, Mount Sion, of which this may be the sense; but Jehovah shall set up the adversaries of Mount Sion against him, (i.e., against Israel), and will strengthen his enemies together; the Syrians, the Philistines, who are called the adversaries of Mount Sion. See Simonis Lex. in voce סכך sachach.

Therefore the LORD shall set up the adversaries of (o) Rezin against him, and join his enemies together;
(o) Rezin king of Syria, who was in league with Israel, was slain by the Assyrians, after whose death, Aram that is, the Syrians were against Israel, who on the other side were assailed by the Philistines.

Therefore the Lord shall set up the adversaries of Rezin against him,.... Set them up on high, as the word (a) signifies; exalt them above him, and make them superior to him, and conquerors of him, meaning the Assyrians; who, being sent for by Ahab, went up against Damascus, took it, and carried the people captive, and slew Rezin the king of Syria, the head of which was Damascus, 2-Kings 16:7 this is mentioned, because the Israelites put great trust and confidence in this prince, with whom they were in alliance; and this is said to abate their pride, arrogance, and haughtiness, before expressed:
and join his enemies together; or mix them; the Assyrian army, consisting of a mixture of various nations; or "stir" them "up", as the Targum; instigate them against him. Some understand the whole of Israel, against whom the adversaries of Rezin, namely, the Assyrians, would come, as they did, and invade their land, and carry them captive; with whom were various other people, as follows.
(a) "elevabit, sive extollet", Forerius.

adversaries of Rezin--the Assyrians, who shall first attack Damascus, shall next advance "against him" (Ephraim). This is the punishment of Ephraim's pride in making light (Isaiah 9:10) of the judgment already inflicted by God through Tiglath-pileser (2-Kings 15:29). A second Assyrian invasion (see on Isaiah 7:1) shall follow. The reading "princes" for "adversaries" in uncalled for.
join--rather, "arm"; cover with armor [MAURER].
his--Rezin's.

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.