8 Then shall the Assyrian fall with the sword, not of a mighty man; and the sword, not of a mean man, shall devour him: but he shall flee from the sword, and his young men shall be discomfited.
(Verse 6 onwards) Return, as you have deeply strayed, O children of Israel. For on that day a man will cast away the idols of his silver and the idols of his gold, which your own hands have made for yourselves to sin. And Assur will fall by the sword, not of a man; and a sword, not of a human, will devour him. He will flee not from the face of the sword, and his young men will become forced labor. His strength will pass away in terror, and his fleeing princes will be filled with fear, says the Lord, whose fire is in Zion and whose furnace is in Jerusalem. LXX: Return, O children of Israel, as you have gone deep into sin. For on that day every man will throw away the idols of his silver and the idols of his gold that your own hands have made for your own sins. And Assyria will fall by the sword, not of a man, and a sword, not of a human, will devour him; he will flee, but not from the face of the sword; his young men will be defeated; they will be surrounded like a wall, and they will be conquered; but whoever flees will be captured. Thus says the Lord: Blessed is he who has offspring in Zion and who has a household in Jerusalem. While the Lord fights against his adversaries on Mount Zion and protects it like a rampart, O children of Israel, turn back! As Symmachus translated it: Repent, you who have strayed from the Lord due to deep counsel and sin. For if you do this, casting aside the golden and silver idols that have been a cause of sin for you, because of which your city was captured, Assyria will fall, from whose fear you now flee, not by the sword of men or the strength of an army, but by the power of God. But it signifies that an angel, by whom 185,000 Assyrians were destroyed in one night. Also, the Assyrian king himself will not flee from the sword of men, but from the wrath of God, so that his young and strong men will become tributaries to the Medes, of whom it is said above, in opposition to Babylon: Behold, I will raise up the Medes against you. And the might of Assyria will pass by with the terror of the Lord, and all its princes will tremble. For the Lord has spoken and promised, and what He has said, He has done: and He who has fire in Zion and a furnace in Jerusalem, so that He may consume His adversaries like straw and wood coming out of Jerusalem. Another thing that is said: On that day, a man will throw away his idols of silver and the rest, it is interpreted in such a way that it testifies that after the return from the Babylonian captivity until the coming of Christ, the children of Israel never worshiped idols. Assyria is also signified in the present place, not by an angel, but by the Medes, because it was the most ancient and once powerful kingdom, which was destroyed after offending the Lord, and served the conquerors. The Nazarenes understand this place thus: O children of Israel, who denied the Son of God with wicked counsel, return to Him and His Apostles. For if you do this, you will cast away all the idols that were previously a sin for you, and the devil will fall to you, not by your strength, but by the mercy of God; and its young men who once fought for it will be subjects of the Church, and all its strength and rock will be passed to it; even the philosophers and every perverse doctrine will turn their backs to the sign of the cross. For the opinion of the Lord is that this should be done: whose fire or light is in Zion and his furnace in Jerusalem. Fire and light are written in Hebrew with the same letters Aleph, Vau, Res; if it is read as Ur, it means fire: if Or, it means light. This is said because for the fire, which Symmachus alone interprets, Aquila and Theodotion translate it as light. But I do not know what is meant by what is read in the Septuagint: They will be surrounded like a wall by rock, and they will be conquered: but whoever flees will be captured. Unless perhaps we can say this, that the young men of the Assyrian king who are to be conquered and captured, are surrounded like a rock, that is, by the strength of the Lord, just as a city is surrounded by a wall. Furthermore, what follows: Blessed is the one who has offspring in Zion, and domestic servants in Jerusalem, we can interpret it in such a way as to say that it agrees with the meaning of this place, that the divine word exhorts those who are fleeing to Egypt to return to Jerusalem and to bear children. To whom such great blessedness is promised, that it may be defended and protected by the help of the Lord. And in another place it is written about it: The glory of this last house shall be greater than the glory of the former (Haggai 2:10). Which can also be referred to the Church, the vision of peace and the watchtower, of which it is written: Glorious things are spoken of you, O city of God (Psalm 87:2). And elsewhere: The streams of the river make glad the city of God (Psalm 46:3). For in it there is fire and a furnace that shall devour the sinners, and shall consume the wood, hay, and stubble; or it is a light and an oven, that the brightness of the righteous, and the punishment of the wicked, may be shown.
[AD 420] Jerome on Isaiah 31:6-9