Albert Barnes Commentary Isaiah 9:11

"Therefore Jehovah will set up on high against him the adversaries of Rezin, and will stir up his enemies," — Isaiah 9:11 (ASV)

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 will 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 will be excited into wild and agitated commotion and will pour down together on the land and devour it. In what way this would be done is specified in (Isaiah 9:12).