Genesis 17:11-14; Genesis 17:27
You are to undergo circumcision, and it will be the sign of the covenant between me and you.
For the generations to come every male among you who is eight days old must be circumcised, including those born in your household or bought with money from a foreigner--those who are not your offspring.
Whether born in your household or bought with your money, they must be circumcised. My covenant in your flesh is to be an everlasting covenant.
Any uncircumcised male, who has not been circumcised in the flesh, will be cut off from his people; he has broken my covenant."
And every male in Abraham's household, including those born in his household or bought from a foreigner, was circumcised with him.