And if a man from another country is living with you, and has a desire to keep the Passover to the Lord, let all the males of his family undergo circumcision, and then let him come near and keep it; for he will then be as one of your people; but no one without circumcision may keep it.
And he made with him the agreement of which circumcision was the sign. And so Abraham had a son, Isaac, and gave him circumcision on the eighth day; and Isaac had a son, Jacob, and Jacob was the father of the twelve heads of the families of Israel.