Rashi: His life will be saved, like one who plunders and profits. He will profit his life! Malbim - the Navi uses this expression, for one goes to the enemy to fight and take booty. His booty will be his life!

Malbim: The king's guards would kill anyone who went out to the Bavliyim. Yirmeyah taught that one who goes out, v'Chayah (the guards will not kill him) va'Chai (the Bavliyim will not kill him).