15 And the Lord said to Abraham, The name of Sara thy wife shall not be called Sara, for Sarah shall be her name: 16 and I will bless her, and I will also give thee a son from her; and I will bless her, and assemblies and kings which have dominion over peoples from her shall be. 17 And Abraham fell upon his face and rejoiced, and said in his heart, Will the son of a hundred years have a child, and Sarah the daughter of ninety years bring forth? 18 And Abraham said before the Lord, O that Yishmael may be established before thee! 19 And the Lord said, In verity Sarah thy wife shall bear thee a son, and thou shalt call his name Izhak; and I will establish My covenant with him for an everlasting covenant to his sons after him.

18 Against hope Abraham believed in hope with the result that he became the father of many nations according to the pronouncement, “so will your descendants be.” 19 Without being weak in faith, he considered his own body as dead (because he was about one hundred years old) and the deadness of Sarah’s womb. 20 He did not waver in unbelief about the promise of God but was strengthened in faith, giving glory to God. 21 He was fully convinced that what God promised he was also able to do. 22 So indeed it was credited to Abraham as righteousness.