Albert Barnes Commentary Jeremiah 4:10

"Then said I, Ah, Lord Jehovah! surely thou hast greatly deceived this people and Jerusalem, saying, Ye shall have peace; whereas the sword reacheth unto the life." — Jeremiah 4:10 (ASV)

Ah, Lord God! — Alas! my Lord Yahweh: an expression of disapproval on Jeremiah’s part. Jeremiah had constantly to struggle against the misgivings of his own melancholy nature, but he never let them prevent him from doing his duty. See the introduction of Jeremiah.

You shall have peace — These words are generally referred to the false prophets; they rather refer to real prophecies of future blessedness promised to the Jews. Jeremiah could not reconcile the doom he was now commanded to pronounce, either with his previous prophecy, or with what he read in the writings of his predecessors. Time only could solve the difficulty. Regarding the struggles of the prophets to understand their own predictions, see (1 Peter 1:10–11).

To the soul — The sword has reached the life. That is, it has inflicted a mortal wound.