12-13 From now on, your family must circumcise every baby boy when he is eight days old. You must even circumcise any man or boy you have as a slave, both those born in your homes and those you buy from foreigners. This will be a sign that my promise to you will last for ever.
14 Any man who isn't circumcised hasn't kept his promise to me and cannot be one of my people.
15 Abraham, your wife's name will now be Sarah instead of Sarai.
16 I will bless her, and you will have a son by her. She will become the mother of nations, and some of her descendants will even be kings.
17 Abraham bowed with his face to the ground and thought, “I am almost a hundred years old. How can I become a father? And Sarah is ninety. How can she have a child?” So he started laughing.
18 Then he asked God, “Why not let Ishmael inherit what you have promised me?”
19 But God answered:No! You and Sarah will have a son. His name will be Isaac, and I will make an everlasting promise to him and his descendants.