Charles Ellicott Commentary Jeremiah 51:56

"for the destroyer is come upon her, even upon Babylon, and her mighty men are taken, their bows are broken in pieces; for Jehovah is a God of recompenses, he will surely requite." — Jeremiah 51:56 (ASV)

The Lord God of recompences ... —The prophet clothes the law of retribution which he has been asserting throughout the chapter with a new majesty by connecting it with a new Divine Name . Jehovah delights, as it were, to manifest Himself in that aspect. He is a God of retribution, Jehovah, and will be true to that title.