Therefore the LORD shall set up the adversaries of Rezin against him, and join his enemies together;
Therefore the Lord shall set up the adversaries of Rezin against him - 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 (note on the beginning of Isaiah 7:1-25) shall follow. The reading 'princes' (sarse) for "adversaries" (tzaree) is uncalled for.
And join, х yªcakceek (H5526), from caakak (H5526), to mix together like thorns (Mercer): akin to sowk]. But the primary meaning is to cover. Translate, arm; cover with armour (Maurer). But cf. in favour of the English version Nahum 1:10, "folden together as thorns:" only that there the mingling of the peoples for together is for their own destruction; but here for Ephraim's.
His enemies together - "his," Ephraim's enemies (Isaiah 9:9), as Isaiah 9:12 shows; for the "Syrians" were not Rezin's enemies, but his subjects.