Genesis 17:9-21

God explained to Abraham, “Your part of the covenant is to obey its terms, you and your descendants throughout the ages. So here is the sign of the covenant that you are to keep, so that it will endure between you and me and your descendants: circumcise every male among you. You must undergo cutting off the flesh of your foreskin as a special sign of the covenant between me and you. Throughout your generations, each male child must be circumcised eight days after his birth. This includes those not of your descendants—those born in your household and foreign-born servants whom you have purchased; they must be circumcised, homeborn and purchased alike. In this way, you will carry in your flesh the sign of my everlasting covenant. Any uncircumcised male who does not have the foreskin of his flesh cut off will be cut off from his people, for he has broken my covenant.” God also said to Abraham: “Concerning your wife Sarai, you are not to call her Sarai anymore, but Sarah, ‘My Princess,’ will be her name. I will wonderfully bless her, and I will certainly give you a son through her. Yes, I will bless her greatly, and she will become a mother of nations; kings of nations will arise among her children!” Then Abraham laughed so hard he fell to the ground, saying to himself, “How in the world can a hundred-year-old man become a father? How can my wife Sarah get pregnant at ninety?” And then he spoke out loud: “O, that Ishmael might prosper with your blessing!” God said, “Listen to me. I promise that you and Sarah will have a son, and you will call him Isaac. I will confirm my everlasting covenant of love with him and his seed. And regarding Ishmael, I have heard your cry and I will indeed bless him. I will cause him to have many, many descendants. He will father twelve rulers, and I will make him into a great nation. But my everlasting covenant relationship is with Isaac, who will be born to you and Sarah about this time next year.”