Albert Barnes Commentary Isaiah 10:26

"And Jehovah of hosts will stir up against him a scourge, as in the slaughter of Midian at the rock of Oreb: and his rod will be over the sea, and he will lift it up after the manner of Egypt." — Isaiah 10:26 (ASV)

And the Lord of hosts will stir up—or will raise up that which will act as a scourge to him.

A scourge for him—that is, that which will punish him. The scourge, or rod, is used to denote severe punishment of any kind. The nature of this punishment is immediately specified.

According to the slaughter of Midian—that is, as the Midianites were defeated and punished. There is reference here, doubtless, to the defeat and slaughter of the Midianites by Gideon, as recorded in Judges 7:24-25. That was signal and entire; and the prophet means to say that the destruction of the Assyrian would also be signal and total.

The country of Midian, or Madian, was on the east side of the Elanitic branch of the Red Sea, but it also extended north along the desert of Mount Seir to the country of the Moabites (see the note at Isaiah 60:6).

At the rock of Oreb—at this rock, Gideon killed the two princes of the Midianites, Oreb and Zeeb (Judges 7:25); and from this circumstance, probably, the name was given to the rock (Leviticus 11:15; Deuteronomy 14:14). It was on the east side of the Jordan.

And as his rod ... —that is, as God punished the Egyptians in the Red Sea.

So will he lift it up after the manner of Egypt—as God overthrew the Egyptians in the Red Sea, so will he overthrow and destroy the Assyrian. By these two comparisons, therefore, the prophet represents the complete destruction of the Assyrian army. In both of these cases, the enemies of the Jews had been completely overthrown, and so it would be in regard to the hosts of the Assyrian.