“Then in the fourth generation they will return here, for the iniquity of the Amorite is not yet complete.” Gen. 15:16
God gives Abram a vision of the future of his descendants, and explains they will be enslaved and oppressed for four hundred years. Then they will return to Canaan and possess the land as God had promised. What is curious is verse 16. It is as if God is not just showing Abram his omniscience by portending his and his descendants’ futures, but explaining, in part, a reason the slavery will last so long, and the reason is not his descendants’ disobedience. Instead, it is the disobedience of another people – the Amorites (of whom Abram was friends with Mamre, who followed him into battle to save Lot). The fact that specific timing is involved eludes to two things: The sovereignty of God and the mercy of God.
The sovereignty of God is shown in illustrating that He is in control of human history and destiny. He is not merely explaining how long the Israelites will be enslaved, but in stating that their freedom will coincide with another event – the complete iniquity of the Amorite – implies that God is overseer of time and history. God intends for his own people – Abram’s descendant’s – to be the ones who subdue the Amorites, at the proper time
At the same time, we see another attribute of God – His mercy on sinners. We see an interesting juxtaposition: The enslavement of God’s chosen people on one hand, and God having mercy on the Amorites, who are committing iniquity, on the other. Really they are both enslaved; the Israelites by the Egyptians, and the Amorites by their own iniquity. God’s statement as to the implied fate of the Amorites is telling; It at once implies they are sinful and unrepentant, and yet He is declaring a pre-determined limit of just how much iniquity He will take (over 400 years!) though in the same breath implying they ultimately will not repent.
Abram must have been thinking “What kind of God is this? He is all-knowing and sovereign, yet His ways are not our ways.” And so Abram’s conception of just who this God is continues to unfold.