Genesis 17:23-27

Then Abraham gathered Ishmael, all the males born in his camp, and the slaves he had bought. So that day Abraham circumcised every man and boy in his camp as God had told him to do. Abraham was ninety-nine years old when he was circumcised. And Ishmael, his son, was thirteen years old when he was circumcised. Abraham and his son were circumcised on the same day. Also on that day all the men in Abraham’s camp were circumcised, including all those born in his camp and all the slaves he had bought from other nations.