Isaiah 31:8,9 - Joseph Benson’s Commentary on the Old and New Testaments

Then shall the Assyrian, &c. When you have cast away your idols, and seriously sought unto God for help; both which things were performed by Hezekiah; fall by the sword, not of a mighty man, &c. Not of any man, mean or mighty, but of an angel. But he shall flee from the sword From, or for fear of, that plague, which so strangely and suddenly destroyed his army. And his young men Hebrew, בחוריו, his choice young men, his guards, and valiant commanders, and soldiers, shall be discomfited Hebrew, למס יהיו, shall be for melting, or shall melt away; a great part of them being destroyed by the angel, and the hearts of the rest melting for fear. And he shall pass to his stronghold Sennacherib shall flee away with all speed from Jerusalem, to his strong city of Nineveh. Or, as it is in the margin, which see. And his princes shall be afraid of the ensign Of the Lord's ensign, which he hath lifted up against them. Or, as וחתו מנס, may be properly rendered, shall be struck with consternation at his flight. Saith the Lord, whose fire is in Zion That is, either, 1st, whose fire is continually burning upon the altar in Zion; a sign that his presence and residence are there. Or, rather, 2d, who is, and will appear to be, in Zion like a fire, to defend his people, and to consume their enemies. Thus God promises that he would be, unto Jerusalem, a wall of fire round about, Zechariah 2:5. See also Zechariah 12:6.