Charles Ellicott Commentary Isaiah 30:31

"For through the voice of Jehovah shall the Assyrian be dismayed; with his rod will he smite [him]." — Isaiah 30:31 (ASV)

Shall the Assyrian be beaten down, which smote with a rod. — Better, and He (Jehovah) shall smite with the rod. Asshur appears as the foremost and most dreaded enemy of Judah. The prediction points to the destruction of the armies of Sennacherib.