Romans 4:16-21

16Therefore, the promise comes by faith, so that it may be by grace and may be guaranteed to all Abraham’s offspring—not only to those who are of the law but also to those who have the faith of Abraham. He is the father of us all.

17As it is written: “I have made you a father of many nations.” Gen. 17:5 He is our father in the sight of God, in whom he believed—the God who gives life to the dead and calls into being things that were not. 18Against all hope, Abraham in hope believed and so became the father of many nations, just as it had been said to him, “So shall your offspring be.” Gen. 15:5 19Without weakening in his faith, he faced the fact that his body was as good as dead—since he was about a hundred years old—and that Sarah’s womb was also dead. 20Yet he did not waver through unbelief regarding the promise of God, but was strengthened in his faith and gave glory to God, 21being fully persuaded that God had power to do what he had promised.