Genesis 17:9-11

9God continued to speak to Abraham. He said, ‘As for you, you must agree to obey me. You must obey the rules of my covenant. You, and all your descendants after you must obey it.

10This is what you and all your descendants must do to obey my covenant: Every male person in your family must be circumcised.

11Your circumcision will show that you have agreed to my covenant with you.