Hebrews 6:16-19

It is very common for people to swear an oath by something greater than themselves, for the oath will confirm their statements and end all dispute. 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! We have this certain hope like a strong, unbreakable anchor holding our souls to God himself. Our anchor of hope is fastened to the mercy seat in the heavenly realm beyond the sacred threshold