Charles Ellicott Commentary Jeremiah 21:7

"And afterward, saith Jehovah, I will deliver Zedekiah king of Judah, and his servants, and the people, even such as are left in this city from the pestilence, from the sword, and from the famine, into the hand of Nebuchadrezzar king of Babylon, and into the hand of their enemies, and into the hand of those that seek their life: and he shall smite them with the edge of the sword; he shall not spare them, neither have pity, nor have mercy." — Jeremiah 21:7 (ASV)

He shall smite them with the edge of the sword. —The words were bold words for the prophet to utter while the king was still on the throne, and urged on by his princes to defy the power of the Chaldean king. In Jeremiah 52:10; Jeremiah 52:24–27 we find their literal fulfilment.