Albert Barnes Commentary Jeremiah 49:31

"Arise, get you up unto a nation that is at ease, that dwelleth without care, saith Jehovah; that have neither gates nor bars, that dwell alone." — Jeremiah 49:31 (ASV)

The wealthy nation – Or, a nation at rest, living securely and in confidence.

Which dwell alone – They dwell alone, that is, have neither alliances with other nations, nor contact by commerce.