Hebrews 6:13-18   13. For when God made promise to Abraham, because he could swear by no greater, he sware by himself, 14. Saying, Surely blessing I will bless thee, and multiplying I will multiply thee. 15. And so, after he had patiently endured, he obtained the promise. 16. For men verily swear by the greater: and an oath for confirmation is to them an end of all strife. 17. Wherein God, willing more abundantly to shew unto the heirs of promise the immutability of his counsel, confirmed it by an oath: 18. That by two immutable things, in which it was impossible for God to lie, we might have a strong consolation, who have fled for refuge to lay hold upon the hope set before us:

Romans 4:13-17   13. For the promise, that he should be the heir of the world, was not to Abraham, or to his seed, through the law, but through the righteousness of faith. 14. For if they which are of the law be heirs, faith is made void, and the promise made of none effect: 15. Because the law worketh wrath: for where no law is, there is no transgression. 16. Therefore it is of faith, that it might be by grace; to the end the promise might be sure to all the seed; not to that only which is of the law, but to that also which is of the faith of Abraham; who is the father of us all, 17. (As it is written, I have made thee a father of many nations,) before him whom he believed, even God, who quickeneth the dead, and calleth those things which be not as though they were.