Genesis 17:19-27

Then God said: “No, Sarah your wife shall bear you a son, and you shall call his name Isaac; I will establish My covenant with him for an everlasting covenant, and with his descendants after him. And as for Ishmael, I have heard you. Behold, I have blessed him, and will make him fruitful, and will multiply him exceedingly. He shall beget twelve princes, and I will make him a great nation. But My covenant I will establish with Isaac, whom Sarah shall bear to you at this set time next year.” Then He finished talking with him, and God went up from Abraham. So 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 foreskins that very same day, as God had said to him. Abraham was ninety-nine years old when he was circumcised in the flesh of his foreskin. And Ishmael his son was thirteen years old when he was circumcised in the flesh of his foreskin. That very same day Abraham was circumcised, and his son Ishmael; and all the men of his house, born in the house or bought with money from a foreigner, were circumcised with him.