Genesis 17:
15 ¶ And God said unto Abraham, As for Sarai thy wife, thou shalt not call her name Sarai, but Sarah shall her name be.
16 And I will bless her, and give thee a son also of her: yea, I will bless her, and she shall be a mother of nations; kings of people shall be of her.
17 Then Abraham fell upon his face, and laughed, and said in his heart, Shall a child be born unto him that is an hundred years old? and shall Sarah, that is ninety years old, bear?
18 And Abraham said unto God, O that Ishmael might live before thee!
19 And God said, Sarah thy wife shall bear thee a son indeed; and thou shalt call his name Isaac: and I will establish my covenant with him for an everlasting covenant, and with his seed after him.
20 And as for Ishmael, I have heard thee: Behold, I have blessed him, and will make him fruitful, and will multiply him exceedingly; btwelve princes shall he beget, and I will make him a great nation.
21 But my covenant will I establish with Isaac, which Sarah shall bear unto thee at this set time in the next year.

Genesis 21:
Genesis 21:
1 And the Lord visited Sarah as he had said, and the Lord did unto Sarah as he had spoken.
2 For Sarah conceived, and bare Abraham a son in his bold age, at the set time of which God had spoken to him.
3 And Abraham called the name of his son that was born unto him, whom Sarah bare to him, Isaac.
4 And Abraham circumcised his son Isaac being eight days old, as God had commanded him.
5 And Abraham was an hundred years old, when his son Isaac was born unto him.
6 ¶ And Sarah said, God hath made me to laugh, so that all that hear will laugh with me.
7 And she said, Who would have said unto Abraham, that Sarah should have given children suck? for I have born him a son in his old age.
8 And the child grew, and was weaned: and Abraham made a great feast the same day that Isaac was weaned.
9 ¶ And Sarah saw the son of Hagar the Egyptian, which she had born unto Abraham, mocking.
10 Wherefore she said unto Abraham, Cast out this bondwoman and her son: for the son of this bondwoman shall not be heir with my son, even with Isaac.
11 And the thing was very grievous in Abraham's sight because of his son.
12 ¶ And God said unto Abraham, Let it not be grievous in thy sight because of the lad, and because of thy bondwoman; in all that Sarah hath said unto thee, hearken unto her voice; for in Isaac shall thy seed be called.
13 And also of the son of the bondwoman will I make a nation, because he is thy seed.
14 And Abraham rose up early in the morning, and took bread, and a bottle of water, and gave it unto Hagar, putting it on her shoulder, and the child, and sent her away: and she departed, and wandered in the wilderness of Beer-sheba.
15 And the water was spent in the bottle, and she cast the child under one of the shrubs.
16 And she went, and sat her down over against him a good way off, as it were a bowshot: for she said, Let me not see the death of the child. And she sat over against him, and lift up her voice, and wept.
17 And God heard the voice of the lad; and the angel of God called to Hagar out of heaven, and said unto her, What aileth thee, Hagar? fear not; for God hath heard the voice of the lad where he is.
18 Arise, lift up the lad, and hold him in thine hand; for I will make him a great nation.
19 And God opened her eyes, and she saw a well of water; and she went, and filled the bottle with water, and gave the lad drink.
20 And God was with the lad; and he grew, and dwelt in the wilderness, and became an archer.
21 And he dwelt in the wilderness of Paran: and his mother took him a wife out of the land of Egypt.