Genesis 15:9-13

So He said to him, “Bring Me a three-year-old heifer, a three-year-old female goat, a three-year-old ram, a turtledove, and a young pigeon.”

Then he brought all these to Him and cut them in two, and laid each half opposite the other; but he did not cut the birds.

And birds of prey came down upon the carcasses, and Abram drove them away.

Now when the sun was going down, a deep sleep fell upon Abram; and behold, terror and great darkness fell upon him.

Then God said to Abram, “Know for certain that your descendants will be strangers in a land that is not theirs, where they will be enslaved and oppressed for four hundred years.