John Gill's Exposition of the Whole Bible
Jeremiah 51:14
The Lord hath sworn by himself, [saying],.... Or, "by his soul" or "life" q; which is himself, than which he cannot swear by a greater, Hebrews 6:13; and the certain performance of what he swears unto need not be doubted of; and indeed the design of the oath is to assure of the truth of the thing, about which, after this, there ought to be no hesitation:
surely I fill thee with men as with caterpillars; or "locusts" r; march in vast numbers, and make sad desolation where they come; and to which a numerous army may fitly be compared; and which are here meant, even the army of Cyrus, that should enter Babylon, and fill it, as it did. So the Targum,
"the Lord of hosts hath sworn by his word, if I fill them with armies of many people as locusts:''
and they shall lift up a shout against thee; as soldiers, when they make the onset in battle; or as besiegers, when they make their attack on a city; or as when grape gatherers bring in their vintage, or tread out their wine, to which the allusion is: it signifies that her enemies should get an entire victory, and triumph over her.
q בנפשו "per animam suam", Pagninus, Cocceius, Schmidt. r כילק "ut, [vel] quasi brucho", V. L. Cocceius, Montanus, Grotius, Schmidt.