Genesis 15:12-16

As the heavy veil of night fell, Abram went into a deep state of sleep, and suddenly a great dreadful darkness surrounded him and he was filled with fear. Then YAHWEH said to Abram, “Know this: your descendants will live as strangers in a foreign country. They will be enslaved and mistreated for four hundred years. Afterward I will punish that nation for enslaving them, and your descendants will come out of slavery with untold wealth. You, however, will go to your ancestors in peace and live a full life. And after the fourth generation, your descendants will return here; for then the sin of the Amorites will be ripe for judgment.”