Thus saith the LORD God of Israel; Behold, I will turn back the weapons of war that are in your hands, wherewith ye fight against the king of Babylon, and against the Chaldeans, which besiege you without the walls, and I will assemble them into the midst of this city.
Thus saith the Lord God of Israel - those "wondrous works" (Jeremiah 21:2) do not belong to you; God is faithful; it is you who forfeit the privileges of the covenant by unfaithfulness. 'God will always remain the God of Israel, though He destroy thee and thy people' (Calvin).
I will turn back the weapons - I will turn them to a very different use from what you intend them. You now with them, fight against the Chaldees "without the walls" (the Jewish defenders being as yet able to sally forth more freely, and defend the fountains outside the walls in the valley under Mount Zion: see Jeremiah 21:13; Jeremiah 19:2; Jeremiah 19:6-7), but soon ye shall be driven back within the city (Maurer).
And I will assemble them into the midst of this city - and "in the midst" of it I will cause all your arms to be gathered in one place by the Chaldean conquerors (Grotius), who shall slay you with those very arms (Menochius).