Albert Barnes Commentary 2 Kings 25:24

"And Gedaliah sware to them and to their men, and said unto them, Fear not because of the servants of the Chaldeans: dwell in the land, and serve the king of Babylon, and it shall be well with you." — 2 Kings 25:24 (ASV)

As rebels against the Babylonian king, their lives were forfeit. Gedaliah pledged to them with an oath that if they provided no further reason for complaint, their past offenses would be forgiven.