Genesis 15:9-17

So the LORD said to him, “Bring me a heifer, a goat and a ram, each three years old, along with a dove and a young pigeon.” Abram brought all these to him, cut them in two and arranged the halves opposite each other; the birds, however, he did not cut in half. Then birds of prey came down on the carcasses, but Abram drove them away. As the sun was setting, Abram fell into a deep sleep, and a thick and dreadful darkness came over him. 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. But I will punish the nation they serve as slaves, and afterward they will come out with great possessions. You, however, will go to your ancestors in peace and be buried at a good old age. In the fourth generation your descendants will come back here, for the sin of the Amorites has not yet reached its full measure.” When the sun had set and darkness had fallen, a smoking firepot with a blazing torch appeared and passed between the pieces.