Albert Barnes Commentary Jeremiah 1:7

"But Jehovah said unto me, Say not, I am a child; for to whomsoever I shall send thee thou shalt go, and whatsoever I shall command thee thou shalt speak." — Jeremiah 1:7 (ASV)

Jeremiah suggested two difficulties: the first, inexperience, and the second, timidity. God now removes the first of these. Inexperience is no obstacle where the duty is simple obedience. His timidity is removed by the promise given him in the next verse.