Romans 4:20

17 (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.

18 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.

19 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;

20 yet, looking unto the promise of God, he wavered not through unbelief, but waxed strong through faith, giving glory to God,

21 and being fully assured that what he had promised, he was able also to perform.

22 Wherefore also it was reckoned unto him for righteousness.

23 Now it was not written for his sake alone, that it was reckoned unto him;