In Ephesians 1:7 we read that when we are in Christ "we have redemption through His blood, the forgiveness of our trespasses." This is all in accordance with "the riches of God's grace." Within this verses we find a powerful metaphor to help us understand our new identity in Christ, and that metaphor is redemption.
Redempton means to purchase on behalf of another. It was a word used in the ancient world to describe when a person would purchase a slaves freedom. It was an exchange, where a price would be arranged by the slave's owner and then paid by the one who was setting the slave free.
This is a perfect picture of what God does for us through Jesus. Before Jesus we were all slaves or in bondage to sin. Before Christ we stood guilty before God with the full consequence of condemnation. But now through the price of Christ's shed blood, God bought us back to be in relationship with Him. The consequence of this exchange is our freedom.
This freedom has several aspects to it. First it is freedom from eternal condemnation. Instead of hell we receive heaven. Instead of an eternity away from God, we now through Christ will be with Him forever and ever. Another aspect of this freedom is from sin itself. Instead of being mastered by our sin nature, we are now set free to live a new way of life.
This is the idea behind Romans 6:20-23, "when you were slaves of sin, you were free in regard to righteousness.... But now that you have been set free from sin, you have become slaves of God... For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord."
There is a story I read several years ago in a Daily Bread that helps us understand this great metaphor of redemption. There was a young boy who built a beautiful model boat which he lost in fast moving stream. One day he was excited to find his lost boat in a downtown store window. He ran into the store and told the owner that that was his boat, to which the owner replied that he could have it back, but he would have to pay one dollar.
The boy ran home counted out his change from a piggy bank and returned back to the store and bought his boat back. Then the story ends with this quote by the little boy, "Now you're twice mine. First, I made you and now I bought you." That pretty much sums up the gospel when we trust in Jesus, God who made us has now bought us back through Christ's shed blood.