Genesis 17:9-14 (New International Version)

 ⁹ Then God said to Abraham, "As for you, you must keep my covenant, you and your descendants after you for the generations to come. ¹⁰ This is my covenant with you and your descendants after you, the covenant you are to keep: Every male among you shall be circumcised. ¹¹ You are to undergo circumcision, and it will be the sign of the covenant between me and you. ¹² 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. ¹³ 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. ¹⁴ Any uncircumcised male, who has not been circumcised in the flesh, will be cut off from his people; he has broken my covenant."