“When a foreigner lives with you and wants to observe the Passover to the Lord, all his males must be circumcised, and then he may approach and observe it, and he will be like one who is born in the land – but no uncircumcised person may eat of it.
Then God gave Abraham the covenant of circumcision, and so he became the father of Isaac and circumcised him when he was eight days old, and Isaac became the father of Jacob, and Jacob of the twelve patriarchs.