Genesis 17:23-25

Revised Standard Version

²³ Then Abraham took Ish′mael his son and all the slaves born in his house or bought with his money, every male among the men of Abraham’s house, and he circumcised the flesh of their foreskins that very day, as God had said to him. ²⁴ Abraham was ninety-nine years old when he was circumcised in the flesh of his foreskin. ²⁵ And Ish′mael his son was thirteen years old when he was circumcised in the flesh of his foreskin.