Genesis 15:11 (KJV)

And he said unto him, Take me an heifer of three years old, and a she goat of three years old, and a ram of three years old, and a turtledove, and a young pigeon.

And he took unto him all these, and divided them in the midst, and laid each piece one against another: but the birds divided he not.

And when the fowls came down upon the carcases, Abram drove them away.

And when the sun was going down, a deep sleep fell upon Abram; and, lo, an horror of great darkness fell upon him.

And he said unto Abram, Know of a surety that thy seed shall be a stranger in a land that is not theirs, and shall serve them; and they shall afflict them four hundred years;