Genesis 15:12-14

12 As the sun was setting, Abram fell into a deep sleep, and a thick and dreadful darkness came over him. 13 Then the Lord said to him, “Know for certain that for four hundred years your descendants will be strangers in a country not their own and that they will be enslaved and mistreated there. 14 But I will punish the nation they serve as slaves, and afterward they will come out with great possessions.