Genesis 16-17 NASB
1 Now Sarai, Abram's wife had borne him no children, and she had an Egyptian maid whose name was Hagar. 2 So Sarai said to Abram, "Now behold, the Lord has prevented me from bearing children. Please go in to my maid; perhaps I will obtain children through her." And Abram listened to the voice of Sarai. 3 After Abram had lived ten years in the land of Canaan, Abram's wife Sarai took Hagar the Egyptian, her maid, and gave her to her husband Abram as his wife. 4 He went in to Hagar, and she conceived; and when she saw that she had conceived, her mistress was despised in her sight. 5 And Sarai said to Abram, "May the wrong done me be upon you. I gave my maid into your arms, but when she saw that she had conceived, I was despised in her sight. May the Lord judge between you and me." 6 But Abram said to Sarai, "Behold, your maid is in your power; do to her what is good in your sight." So Sarai treated her harshly, and she fled from her presence.
1 Now when Abram was ninety-nine years old, the Lord appeared to Abram and said to him,
15 Then God said to Abraham, "As for Sarai your wife, you shall not call her name Sarai, but Sarah shall be her name. 16 I will bless her, and indeed I will give you a son by her. Then I will bless her, and she shall be a mother of nations; kings of peoples will come from her." 17 Then Abraham fell on his face and laughed, and said in his heart, "Will a child be born to a man one hundred years old? And will Sarah, who is ninety years old, bear a child?" 18 And Abraham said to God, "Oh that Ishmael might live before You!" 19 But God said, "No, but Sarah your wife will bear you a son, and you shall call his name Isaac; and I will establish My covenant with him for an everlasting covenant for his descendants after him. 20 As for Ishmael, I have heard you; behold, I will bless him, and will make him fruitful and will multiply him exceedingly. He shall become the father of twelve princes, and I will make him a great nation. 21 But My covenant I will establish with Isaac, whom Sarah will bear to you at this season next year." 22 When He finished talking with him, God went up from Abraham.