וְנָפַ֤ל אַשּׁוּר֙ בְּחֶ֣רֶב לֹא־אִ֔ישׁ וְחֶ֥רֶב לֹֽא־אָדָ֖ם תֹּֽאכֲלֶ֑נּוּ וְנָ֥ס לוֹ֙ מִפְּנֵי־חֶ֔רֶב וּבַחוּרָ֖יו לָמַ֥ס יִהְיֽוּ׃
Then shall Asshur fall with the sword, not of man, And the sword, not of men, shall devour him; And he shall flee from the sword, And his young men shall become tributary.
Read midrashic interpretation of Isaiah 31:8: and classical rabbinic exegesis.