Genesis 17:9-15

9Then God said to Abraham, “As for you, you must keep my covenant, you and your descendants after you for the generations to come. 10This is my covenant with you and your descendants after you, the covenant you are to keep: Every male among you shall be circumcised. 11You are to undergo circumcision, and it will be the sign of the covenant between me and you. 12For 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. 13Whether born in your household or bought with your money, they must be circumcised. My covenant in your flesh is to be an everlasting covenant.

14Any uncircumcised male, who has not been circumcised in the flesh, will be cut off from his people; he has broken my covenant.” 15God also said to Abraham, “As for Sarai your wife, you are no longer to call her Sarai; her name will be Sarah.