Genesis 15:14

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;

And thou shalt go to thy fathers in peace; thou shalt be buried in a good old age.

But in the fourth generation they shall come hither again: for the iniquity of the Amorites is not yet full.