Genesis 17:9-14

God continued to Abraham, “And you: You will honor my covenant, you and your descendants, generation after generation. This is the covenant that you are to honor, the covenant that pulls in all your descendants: Circumcise every male. Circumcise by cutting off the foreskin of the penis; it will be the sign of the covenant between us. Every male baby will be circumcised when he is eight days old, generation after generation—this includes house-born slaves and slaves bought from outsiders who are not blood kin. Make sure you circumcise both your own children and anyone brought in from the outside. That way my covenant will be cut into your body, a permanent mark of my permanent covenant. An uncircumcised male, one who has not had the foreskin of his penis cut off, will be cut off from his people—he has broken my covenant.”