In his book, Scandalous, D. A. Carson has a helpful discussion of the concept of redemption and its use in the ancient world —
In our world a word like redemption belongs to God-talk. In other words you normally do not talk fluently about redemption in everyday life. Redemption is something religious people talk about. Until fairly recent times, however — and still in some sectors — redemption was frequently used in an economic sense. For instance, you might redeem a mortgage. People do not speak of “redemption money” anymore, but they did a bare fifty or sixty years ago, when there were a lot more pawn shops around. If you needed some money in the great depression, you hawk a watch. You would sell it to the pawn shop. They would keep for three weeks or six months or whatever agreed time period before they would sell it, and in that time you could go back and redeem it; that you could pay money to have it freed (the amount for which you sold it plus a percentage) — to have it released so that you could have it again. You could redeem your watch.
In the ancient world, redemption language was common. Of course it is found in Scripture (e.g., God redeems Israel from slavery), but it was common economic language in the Greco-Roman world. It was a word commonly used on the streets in any imperial city. It was used, for example, for the redemption of slaves. In the ancient world you might become a slave as a result of losing a war or because marauding parties attacked your territory and captured you and your family. But sometimes in the ancient world you became a slave because of economic circumstances. There were no bankruptcy laws to protect you — no chapter eleven or chapter thirteen (to use categories that are familiar to Americans). So suppose you borrow some money to start a business, and you lose your shirt during an economic downturn. What do you do? You sell yourself and maybe your whole family into slavery There is nothing else you can do. So many people became slaves in the ancient world as a result of bankruptcy.
But suppose that you have a well-to-do cousin twenty-live miles away (a day’s journey) who hears that you have sold yourself into slavery. Not only is this cousin well-to-do; he is pretty decent. So he decides to buy you back. He redeems you. He travels a day’s journey to where you have become a slave, and he makes an arrangement with your owner. There was adequate provision for this under the law. The way it normally worked was like this: the redeemer paid the price money for the slave to a pagan temple plus a small cut for the temple priests (and how small a cut was variable!). Then the temple paid the price money to the owner of the slave, and the slave was then transferred to the ownership of this temple’s god. Thus, the slave was redeemed from the slavery to the slave owner, in order to become a slave to the god. Of course, if you are a slave to a pagan god, that basically means that you are free and can do anything you want. It was in part a legal fiction in order to say that the person does not lose his slave status but nevertheless is freed from slavery in the human sphere because the price has been paid. The man has now been redeemed.
Paul picks up that language and says that Christians have been redeemed from slavery to sin, but as a result of this, they have become slaves of Jesus Christ (see Romans 6). Many of our English translations say “servant of Jesus Christ,” but the word most commonly used is doulos, which always refers to a slave. We are slaves of Jesus Christ. We have been redeemed from slavery to sin. Somebody has paid the price. We sing it: we have been “redeemed by the blood of the Lamb.”
We are justified freely by grace, Paul writes, “through the redemption that came by Christ Jesus” (3:24). The slave cannot buy his own freedom; otherwise he would not be a slave. He cannot save himself!