Charles Ellicott Commentary Isaiah 13:2

"Set ye up an ensign upon the bare mountain, lift up the voice unto them, wave the hand, that they may go into the gates of the nobles." — Isaiah 13:2 (ASV)

Lift ye up a banner upon the high mountain... — Strictly speaking, a bare mountain, where there were no trees to hide the standard around which the forces that the prophet sees were to rally. The word and thought are the same as in Isaiah 5:26; but there the summons is for the invaders of Israel, here for its avengers. The voice that summons is, as the next verse shows, that of Jehovah. The “shaking the hand” is, as in Isaiah 10:32, the act of the generals pointing with emphatic gesture to the city that is to be destroyed.

The gates of the nobles. — The word is used to heighten the contrast between the greatness of the city to be destroyed, with its gates that had witnessed for centuries the entrance of kings and princes, and the wild roughness of the barbarian destroyers.