1 And when Abram was ninety-nine years old, the LORD appeared to Abram and said to him, "I am the Almighty God. Walk before me and be perfect.
2 And I will make my covenant between me and you and will multiply you exceedingly."
3 And Abram fell on his face, and God talked with him, saying,
4 "As for me, behold, my covenant is with you, and you shall be a father of many nations.
5 Your name shall no longer be called Abram, but your name shall be Abraham, because a father of many nations I have made you.
6 And I will make you exceedingly fruitful and I will make nations of you, and kings shall proceed from you. 7 And I will establish my covenant between me and you and your seed after you, in their generations, for an everlasting covenant, to be a God to you and to your seed after you. 8 And I will give to you and to your seed after you the land in which you are a stranger, all the land of Canaan, for an everlasting possession. And I will be their God."
9 And God said to Abraham, "You shall keep my covenant therefore—you and your seed after you in their generations. 10 This is my covenant which you shall keep between me and you and your seed after you: every male-child among you shall be circumcised. 11 And you shall circumcise the flesh of your foreskin, and it shall be a token of the covenant between me and you. 12 And he who is eight days old shall be circumcised among you, every male-child in your generations, he who is born in the house, or bought with money of any stranger who is not of your seed. 13 He who is born in your house and he who is bought with your money must be circumcised. And my covenant shall be in your flesh for an everlasting covenant. 14 And the uncircumcised male-child, whose flesh of his foreskin is not circumcised, that soul shall be cut off from his people. He has broken my covenant."
15 And God said to Abraham, "As for Sarai your wife, you shall not call her name Sarai, but Sarah shall be her name. 16 And I will bless her and give you a son also by her. I will even bless her, and she shall be a mother of nations. Kings of people shall proceed from her." 17 Then Abraham fell upon his face and laughed and said in his heart, "Shall a child be born to him who is one hundred years old? And shall Sarah, who is ninety years old, bear?" 18 And Abraham said to God, "O that Ishmael might live before you!" 19 And God said, "Sarah your wife shall bear you a son indeed, and you shall 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 you. Behold, I have blessed him and will make him fruitful and will multiply him exceedingly. Twelve princes he shall beget, and I will make him a great nation. 21 But my covenant I will establish with Isaac, whom Sarah shall bear to you at this set time in the next year." 22 And he ceased talking with him, and God went up from Abraham.
23 And Abraham took Ishmael his son, all who were born in his house, and all who were bought with his money, every male among the men of Abraham's house, and circumcised the flesh of their foreskin, in the same day, as God had said to him. 24 And Abraham was ninety-nine years old when he was circumcised in the flesh of his foreskin. 25 And Ishmael his son was thirteen years old when he was circumcised in the flesh of his foreskin. 26 In the same day Abraham and Ishmael his son were circumcised. 27 And all the men of his house, born in the house and bought with money of the stranger, were circumcised with him.
[v.5] - Quoted in Romans 4:17.
[v.7-8] - Quoted in Galatians 3:16.
[v.8] - Reference, Genesis 12:7.