How do we know God's promises are lasting?

The eternal nature of God's promises is rooted in His immutable character. In James 1:17, we see that all good and perfect gifts come from the Father of lights, in whom there is no variation or shadow due to change. This passage reinforces the idea that because God does not change, His promises remain true and dependable. For believers, this means that our salvation, secured by His divine decree, is guaranteed. His mercy and grace towards us will persist, regardless of our failings, because His disposition towards us is anchored in His unchanging nature. Therefore, knowing that God is immutable helps us rest in the assurance that His promises will always stand.