Genesis 17:10-14

“This is my covenant, which you shall keep, between me and you and your offspring after you. Every male among you shall be circumcised. You shall be circumcised in the flesh of your foreskin. It will be a token of the covenant between me and you. He who is eight days old will be circumcised among you, every male throughout your generations, he who is born in the house, or bought with money from any foreigner who is not of your offspring. He who is born in your house, and he who is bought with your money, must be circumcised. My covenant will be in your flesh for an everlasting covenant. The uncircumcised male who is not circumcised in the flesh of his foreskin, that soul shall be cut off from his people. He has broken my covenant.””