A Seed To Be In Bondage

Genesis 15:7-16

7  And he said unto him, I am the LORD that brought thee out of Ur of the Chaldees, to give thee this land to inherit it. 
8  And he said, Lord GOD, whereby shall I know that I shall inherit it? 
9  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. 
10  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. 
11  And when the fowls came down upon the carcases, Abram drove them away. 
12  And when the sun was going down, a deep sleep fell upon Abram; and, lo, an horror of great darkness fell upon him. 
13  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; 
14  And also that nation, whom they shall serve, will I judge: and afterward shall they come out with great substance. 
15  And thou shalt go to thy fathers in peace; thou shalt be buried in a good old age. 
16  But in the fourth generation they shall come hither again: for the iniquity of the Amorites is not yet full.