At the centre of the message of the Bible is a God who keeps his word. When he makes a promise, we can certainly count on him to fulfill it.
God promised a Redeemer right after our first parents sinned. The entire story line of the scriptures is basically how this promise was realized. And within this general theme there are a whole lot of other promises.
For instance, the promise of a son to Abraham, the promise to deliver the Israelites out of Egypt, the promise to bring them into their own land, the promise of restoration to their land after exile. All were fulfilled.
The Christian today is someone hanging on to another promise: a promise of final salvation through Christ. Interestingly, this is not a promise entirely in the future.
It is a promise God daily fulfills.