Acts 7:6-8

6God told Abraham that his descendants would be foreigners living in another country and that the people there would make them slaves and mistreat them for 400 years.

7God also told him, ‘I will punish the people whom they will serve. After that, they will leave that country and worship me here.’

8“God gave Abraham circumcision to confirm his promise. So when Abraham’s son Isaac was born, Abraham circumcised him on the eighth day. Isaac did the same to his son Jacob, and Jacob did the same to his twelve sons (the ancestors of our tribes).