So then it depends not on human will or exertion, but on God, who has mercy. (ESV)
I love hearing people tell of how God brought them to faith in Jesus Christ. Some Christians tell of how their life was full of self-destruction and reckless living. There is no earthly reason why they should even be alive, and yet they were radically transformed by the power of God. People who have dramatic testimonies often describe how God protected, guided, and drew them to himself.
There is no question that God graciously chooses people to belong to him. It is out of his great love that he is willing to save any. What is this gracious choosing of God based upon? Many would argue that God sees our reaching for him and responds to our act of the will and then chooses us to belong to the Kingdom of God.
Paul seems to be saying something quite different in this verse. Paul says that it (God's gracious choosing of people for salvation) does not depend on human will or exertion. Salvation is a work of God, initiated by God. We are not saved because we are so clever and have decided that God is deserving of our wonderful works.
We are saved because God, who is rich in mercy, chose us. He sent his Son to the cross to take the penalty for our sin, and to conquer death for us so that we could also be with him for eternity. Because this salvation is based in the sovereign will of God consider who should get the glory for this amazing work. May God get all the glory!
Our works mean nothing to the Lord. He chooses us to belong to him, provides us with the means of salvation, and gives us the faith which is necessary to believe in him. Repentance and belief are the appropriate responses to the work that God has done to make us his own. Praise his name.