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 34:7

34:7 He did this while the army of the king of Babylon was attacking Jerusalem and the cities of Lachish and Azekah. He was attacking these cities because they were the only fortified cities of Judah which were still holding out.