John Gill Commentary Jeremiah 42:11

"Be not afraid of the king of Babylon, of whom ye are afraid; be not afraid of him, saith Jehovah: for I am with you to save you, and to deliver you from his hand." — Jeremiah 42:11 (ASV)

Be not afraid of the king of Babylon, of whom you are afraid, &c.] Lest he should revenge the death of Gedaliah upon them, which was a groundless fear; see (Jeremiah 41:18); or that they should be dealt hardly with by him, and be cruelly oppressed, and not able to live in subjection to him; see (Jeremiah 40:9);

be not afraid of him, saith the Lord: who, being omniscient, knew they were; and, being omnipotent, a greater King than the king of Babylon, the King of kings, they had no reason to fear anything from him, since they were under his protection:

for I [am] with you to save you, and to deliver from his hand; from his avenging and oppressing hand; though they were not to be delivered as yet from subjection to him, or being tributaries to him; which they might be, and yet dwell in peace and safety.