Hebrews 6:17-18

So in the same way, God wanted to end all doubt and confirm it even more forcefully to those who would inherit his promises. His purpose was unchangeable, so God added his vow to the promise. So it is impossible for God to lie for we know that his promise and his vow will never change! And now we have run into his heart to hide ourselves in his faithfulness. This is where we find his strength and comfort, for he empowers us to seize what has already been established ahead of time—an unshakable hope!