This verse is in essence a repetition of portions from 1.18-19. See there. Here the metaphor I will make you to this people a fortified wall of bronze can be expressed as “I will make you safe from the attack of the people, like a wall strengthened with bronze” or “If the people try to harm you, it will be like attacking a wall fortified with bronze.”

Good News Translation has shifted says the LORD to the end of verse 21. Translators in many other languages will find this more natural as well. See 1.8.

Quoted with permission from Newman, Barclay M. and Stine, Philip C. A Handbook on Jeremiah. (UBS Helps for Translators). New York: UBS, 2003. For this and other handbooks for translators see here .