Jeremiah 1:18

1:18 I, the Lord, hereby promise to make you as strong as a fortified city, an iron pillar, and a bronze wall. You will be able to stand up against all who live in the land, including the kings of Judah, its officials, its priests and all the people of the land.

Jeremiah 11:4

11:4 Those are the terms that I charged your ancestors to keep when I brought them out of Egypt, that place which was like an iron-smelting furnace. I said at that time, “Obey me and carry out the terms of the agreement exactly as I commanded you. If you do, you will be my people and I will be your God.

Jeremiah 29:26

29:26 “The Lord has made you priest in place of Jehoiada. He has put you in charge in the Lord’s temple of controlling any lunatic who pretends to be a prophet. And it is your duty to put any such person in the stocks with an iron collar around his neck.