Genesis 17:24-27

‘And 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. In the selfsame day was Abraham circumcised and Ishmael his son, and all the men of his house, those born in the house and those bought with wealth from the stranger, were circumcised with him.'

Ishmael is mentioned separately as one named in the covenant. His age shows that he is at the beginning of manhood and thus old enough to participate in a covenant meaningfully. So ends another covenant record. But this time a covenant including Ishmael and offered to a number of nations. It is significant that the circumcision of the final one of the trio, Isaac, is also recorded. It is found in Genesis 21:4, the only other mention in Genesis of an individual's circumcision.