Acts 7:6-8

6And this is, in effect, what God spoke [to him]: That his descendants would be aliens (strangers) in a foreign land, and that they would be enslaved and mistreated for four hundred years.

7‘And I will judge any nation to whom they will be in bondage,’ said God, ‘and after that they will come out and serve Me [in worship] in this place.’

8And God gave Abraham a covenant [a formal agreement to be strictly observed] of [which] circumcision [was the sign]; and so [under these circumstances] Abraham became the father of Isaac, and circumcised him on the eighth day; and Isaac [became the father] of Jacob, and Jacob [became the father] of the twelve patriarchs.