Acts 7:6-8

God spoke with him and gave him this promise: ‘Your descendants will live in a foreign land with a people who will make slaves of them and oppress them for four hundred years. But I will judge the nation that enslaves them, and your descendants will be set free to return to this land to serve and worship me.’ “Then God entered into covenant with Abraham, which included the requirement of circumcision. So when he became the father of Isaac, he circumcised him eight days after his birth.