His life — This is a proverbial expression, signifying a man's possession of his life as a prey, or booty recovered from the enemy.
Related Commentaries of Jeremiah 21:9
Jeremiah 21:9
9 He that abideth in this city shall die by the sword, and by the famine, and by the pestilence: but he that goeth out, and falleth to the Chaldeans that besiege you, he shall live, and his life shall be unto him for a prey.