Jeremiah 49:13 - Matthew Poole's English Annotations on the Holy Bible

As men, when they would confirm their promise or threatening to do any thing, add an oath to it, so doth God, who, having no greater to swear by, swears by himself, Jeremiah 44:26. That which God would here confirm was his threatening against Edom, expressed under the notion of Bozrah, (a part for the whole,) Bozrah being its principal city, Isaiah 63:1, as well as a city of Moab (as we found in the foregoing chapter); and that which he threatens it with was not being a reproach, a waste, and a curse for a time, but for ever.