Romans 4:16-21

For this cause it is of faith, that it may be according to grace; to the end that the promise may 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 (as it is written, A father of many nations have I made thee) before him whom he believed, even God, who giveth life to the dead, and calleth the things that are not, as though they were. Who in hope believed against hope, to the end that he might become a father of many nations, according to that which had been spoken, So shall thy seed be. And without being weakened in faith he considered his own body now as good as dead (he being about a hundred years old), and the deadness of Sarah’s womb; yet, looking unto the promise of God, he wavered not through unbelief, but waxed strong through faith, giving glory to God, and being fully assured that what he had promised, he was able also to perform.