Not a single one of all the good promises the Lord had given to the family of Israel was left unfulfilled; everything he had spoken came true.
Joshua 21:45 NLT
When paper currency first came into use everyone new that it wasn’t worth the paper it was written on. The paper wasn’t the important part – it was the promise that was written on it: I promise to pay the bearer on demand the sum of £1 sterling. Whoever had the note had a promise that would be kept – turn up at the Bank of England, hand over the note and you will be given silver (sterling) to the value of the note.
That doesn’t work now.
God’s promises are different. They are eternal. They are always kept.