Genesis 17:23-26

   23: And Abraham took Ishmael his son, and all that were born in his house, and all that were bought with his money, every male among the men of Abraham's house; and circumcised the flesh of their foreskin in the selfsame day, as God had said unto him.
   24: And Abraham was ninety years old and nine, when he was circumcised in the flesh of his foreskin.
   25: And Ishmael his son was thirteen years old, when he was circumcised in the flesh of his foreskin.
   26: In the selfsame day was Abraham circumcised, and Ishmael his son.