Genesis 17:9-14

⁹And God said to Abraham, "As for you, you shall keep my covenant, you and your descendants after you throughout their generations. ¹⁰This is my covenant, which you shall keep, between me and you and your descendants after you: Every male among you shall be circumcised. ¹¹You shall be circumcised in the flesh of your foreskins, and it shall be a sign of the covenant between me and you. ¹²He that is eight days old among you shall be circumcised; every male throughout your generations, whether born in your house, or bought with your money from any foreigner who is not of your offspring, ¹³both he that is born in your house and he that is bought with your money, shall be circumcised. So shall my covenant be in your flesh an everlasting covenant. ¹⁴Any uncircumcised male who is not circumcised in the flesh of his foreskin shall be cut off from his people; he has broken my covenant."