Rashi on Isaiah
Woe to a multitude of many peoples This is a principle followed throughout all generations; the scourge by which Israel is punished, shall eventually suffer. Therefore, the prophets who prophesy Israel’s retribution through the nations, juxtapose after it the retribution of the nation by which Israel was punished.
Ibn Ezra on Isaiah
Woe to the multitude of many people, that is, to the king of Assyria and his army, coming against Zion.