Charles Ellicott Commentary Jeremiah 40:9

"And Gedaliah the son of Ahikam the son of Shaphan sware unto them and to their men, saying, Fear not to serve the Chaldeans: dwell in the land, and serve the king of Babylon, and it shall be well with you." — Jeremiah 40:9 (ASV)

Fear not to serve the Chaldeans ... —Gedaliah, acting as Satrap of the province, assures them that, though they had fought against the conquerors, there would be a full amnesty, and that they might therefore banish all fears of being maltreated. He will remain at his post, and they may return to their own homes.