There is the saying “As good as his word”.
God is God. All God has to do to guarantee His promise to us to give us His word. When He says it, we can count on it. No ifs, ands or buts. It is done.
I can take it to the bank. He won’t break His promise to me. He is faithful so I can be faithful.
When God wanted to guarantee his promises, he gave his word, a rock-solid guarantee—God can’t break his word. And because his word cannot change, the promise is likewise unchangeable. Hebrews 6:18