Genesis 15:12-16

As the sun was setting, Abram fell into a deep sleep, and everything became dark and frightening. Then the LORD said: Abram, you will live to an old age and die in peace. But I solemnly promise that your descendants will live as foreigners in a land that doesn't belong to them. They will be forced into slavery and abused for four hundred years. But I will terribly punish the nation that enslaves them, and they will leave with many possessions. Four generations later, your descendants will return here and take this land, because only then will the people who live here be so sinful that they deserve to be punished.