Genesis 17:15-21

Isaac’s Birth Promised

15And God said to Abraham, “As for Sarai your wife, you shall not call her name Sarai, but Sarah
 Sarai and  Sarah mean princess
shall be her name.
16I will bless her, and moreover, I will bgive
Hebrew have given
you a son by her. I will bless her, and dshe shall become nations; kings of peoples shall come from her.”
17Then Abraham efell on his face fand laughed and said to himself, “Shall a child be born to a man who is a hundred years old? Shall Sarah, who is ninety years old, bear a child?” 18And Abraham said to God, “Oh that Ishmael might live before you!” 19God said, “No, but gSarah your wife shall bear you a son, and you shall call his name hIsaac.
 Isaac means he laughs
I will establish my covenant with him as an everlasting covenant for his offspring after him.
20As for Ishmael, I have heard you; behold, I have blessed him and will make him fruitful and jmultiply him greatly. He kshall father twelve princes, and lI will make him into a great nation. 21But mI will establish my covenant with Isaac, nwhom Sarah shall bear to you at this time next year.”

Genesis 18:11-14

11Now oAbraham and Sarah were old, advanced in years. The way of women had ceased to be with Sarah. 12 pSo Sarah laughed to herself, saying, qAfter I am worn out, and rmy lord is old, shall I have pleasure?” 13The Lord said to Abraham, “Why did Sarah laugh and say, ‘Shall I indeed bear a child, now that I am old?’ 14 sIs anything too hard
Or wonderful
for the Lord? uAt the appointed time I will return to you, about this time next year, and Sarah shall have a son.”

Genesis 21:1-2

The Birth of Isaac

1The Lord vvisited Sarah as he had said, and the Lord did to Sarah was he had promised. 2And Sarah xconceived and bore Abraham a son in his old age yat the time of which God had spoken to him.
Copyright information for ESV