Old Testament? This is the most important part:

10 This is my covenant with you and your descendants after you, the covenant you are to keep: Every male among you shall have their genitals mutilated. 11 You are to cut off the foreskin of your penis, 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 have his penis mutilated, including those born in your household or slaves 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 have their genitals mutilated. My covenant in your flesh is to be an everlasting covenant. 14 Any natural male, who has not cut off part of his penis, will be cut off from his people; he has broken my covenant.”