No weapon forged against you will defeat you

No weapon forged against you will defeat you
"But nobody can make a weapon that will beat you when your enemies attack you. If people accuse you of bad things, you will show that they are wrong. That is what the LORD will do as a gift for his servants. Yes, I will show that they are right.’ That is what the LORD says. Isaiah 54:17 EASY

Here's some background from The Message Bible translation.
“Afflicted city, storm-battered, unpitied: I’m about to rebuild you with stones of turquoise, Lay your foundations with sapphires, construct your towers with rubies, Your gates with jewels, and all your walls with precious stones.

All your children will have GOD for their teacher— what a mentor for your children! You’ll be built solid, grounded in righteousness, far from any trouble—nothing to fear! far from terror—it won’t even come close! If anyone attacks you, don’t for a moment suppose that I sent them - 

And if any should attack, nothing will come of it. I create the blacksmith who fires up his forge and makes a weapon designed to kill. I also create the destroyer— but no weapon that can hurt you has ever been forged. Any accuser who takes you to court will be dismissed as a liar. This is what GOD’s servants can expect. I’ll see to it that everything works out for the best.” GOD’s Decree. Isaiah 54:11-17 MSG