Romans 4:12-13

and [that he would be] the [spiritual] father of those circumcised who are not only circumcised, but who also walk in the steps of the faith of our father Abraham which he had before he was circumcised. For the promise to Abraham or to his descendants that he would be heir of the world was not through [observing the requirements of] the Law, but through the righteousness of faith. [Gen 17:4-6; 22:16-18]