Romans 4:18

‘Who in hope believed against hope, to the end that he might become a father of many nations, according to what had been spoken, “So shall your seed be.” ’

Paul now makes the application to what followed in the life of Abraham, something which also resulted from his faith. For as a consequence of God’s promise he believed that he would be the father of many nations, even though it was ‘a hope believed against hope’, that is, a hope in what appeared to be impossible. He believed God’s promise that ‘so will your seed be’. Note that the citation is from Genesis 15:5 which was, of course, immediately followed by the statement that God reckoned Abraham as ‘in the right’ because of his faith.