Genesis 17:23-27

Then Abraham took Ishmael his son, and all the servants who were born in his house and all who were purchased with his money, every male among the men of Abraham’s household, and circumcised the flesh of their foreskin the very same day, as God had said to him. So Abraham was ninety-nine years old when he was circumcised. And Ishmael his son was thirteen years old when he was circumcised. On the very same day Abraham was circumcised, as well as Ishmael his son. All the men [servants] of his household, both those born in the house and those purchased with money from a foreigner, were circumcised along with him [as the sign of God’s covenant with Abraham].