Romans 4:13 (WEB)
For the promise to Abraham and to his offspring that he would be heir to the world wasn't through the law, but was through the righteousness of faith.
Romans 4:16, 16 That is why it depends on faith, in order that the promise may rest on grace and be guaranteed to all his offspring—not only to the adherent of the law but also to the one who shares the faith of Abraham, who is the father of us all, - ESV
Romans 4:17 (WEB)
As it is written "I have made you a father of many nations," Ths is in the presence of him whom he believed: God, who gives life to the dead, and calls things that are not, as though they were.
Romans 4:18 (WEB)
Against hope, Abraham in hope believed to the end that he might become the father of many nations, according to that which had been spoken, "So will your offspring be."
Romans 4:19, 19 He did not weaken in faith when he considered his own body, which was as good as dead because he was about a hundred years old, or when he considered the barrenness of Sarah’s womb. - RSV