Whole chapter discussed by Augustine of Hippo, Martin Luther —
Abraham to Father Many Nations
1When Abram was ninety-nine years old, the LORD appeared to him and said, “I am God Almighty. Walk before Me and be blameless. 2I will establish My covenant between Me and you, and I will multiply you exceedingly.”
3Then Abram fell facedown, and God said to him, 4“As for Me, this is My covenant with you: You will be the father of many nations. 5No longer will you be called Abram, but your name will be Abraham, for I have made you a father of many nations.
6I will make you exceedingly fruitful; I will make nations of you, and kings will descend from you.
7I will establish My covenant as an everlasting covenant between Me and you and your descendants after you, to be your God and the God of your descendants after you.
8And to you and your descendants I will give the land where you are residing—all the land of Canaan—as an eternal possession; and I will be their God.”
The Covenant of Circumcision
9God also said to Abraham, “You must keep My covenant—you and your descendants in the generations after you. 10This is My covenant with you and your descendants after you, which you are to keep: Every male among you must be circumcised. 11You are to circumcise the flesh of your foreskin, and this will be a sign of the covenant between Me and you.
12Generation after generation, every male must be circumcised when he is eight days old, including those born in your household and those purchased from a foreigner—even those who are not your offspring. 13Whether they are born in your household or purchased, they must be circumcised. My covenant in your flesh will be an everlasting covenant.
14But if any male is not circumcised, he will be cut off from his people; he has broken My covenant.”
15Then God said to Abraham, “As for Sarai your wife, do not call her Sarai, for her name is to be Sarah. 16And I will bless her and will surely give you a son by her. I will bless her, and she will be the mother of nations; kings of peoples will descend from her.”
17Abraham fell facedown. Then he laughed and said to himself, “Can a child be born to a man who is a hundred years old? Can Sarah give birth at the age of ninety?” 18And Abraham said to God, “O that Ishmael might live under Your blessing!”
19But God replied, “Your wife Sarah will indeed bear you a son, and you are to name him Isaac. I will establish My covenant with him as an everlasting covenant for his descendants after him. 20As for Ishmael, I have heard you, and I will surely bless him; I will make him fruitful and multiply him greatly. He will become the father of twelve rulers, and I will make him into a great nation. 21But I will establish My covenant with Isaac, whom Sarah will bear to you at this time next year.”
22When He had finished speaking with Abraham, God went up from him.
23On that very day Abraham took his son Ishmael and all those born in his household or purchased with his money—every male among the members of Abraham’s household—and he circumcised them, just as God had told him.
24So Abraham was ninety-nine years old when he was circumcised, 25and his son Ishmael was thirteen; 26Abraham and his son Ishmael were circumcised on the same day. 27And all the men of Abraham’s household—both servants born in his household and those purchased from foreigners—were circumcised with him.