21 But what fruit were you getting at that time from the things of which you are now ashamed? For the end of those things is death.
22 But now that you have been set free from sin and have become slaves of God, the fruit you get leads to sanctification and its end, eternal life.
Verse 20 reminds the Roman believers of their pre-Christian lives. It is the flipside of verse 18, where Paul tells them they were set free from sin and have become slaves of righteousness. Once again the slavery metaphor helps Paul make the point that sin and righteousness are mutually exclusive. Each person can serve only one master at a time. When the Roman Christians served sin they were free of any obligation to serve righteousness.
Jesus said, “No one can serve two masters, for either he will hate the one and love the other, or he will be devoted to the one and despise the other” (Matthew 6:23–24). RC Sproul refers to Augustine’s remark that a human being is like a horse that can have only one of two riders, Satan or Christ. “Before you were justified, Satan was riding the horse. Now that you are justified, Christ is riding the horse.” Paul exhorts believers not to let Satan back on the horse.Called to be slaves of God
In this era we object to anyone calling us a “slave,” but more than a few members of the Roman church were themselves slaves or former slaves and could well understand Paul’s point. In fact, every Christian is a slave of our glorious Master. In the opening verse of this epistle, Paul introduced himself as a slave of Jesus Christ, and Jesus elevated the dignity of this title for his followers by taking on the nature of a slave (doulos) in his death for us (Philippians 2:7–8).
Notice the layers of irony and paradox: the Lord became a slave to set us free to become slaves of our Lord. Jesus also called us to be slaves of one another: “whoever would be first among you must be your slave” (Matthew 20:27).Shameful past, holy present
Verse 21 points to the dramatic change of perspective Christians have when looking back at our pre-Christian behavior. We know exactly what Paul is talking about, because we understand now how trivial and contemptible was the “fruit” of our former lifestyle. We thought we were fulfilling legitimate needs in the best way possible and could not imagine a better way to live. Now walking in the light of the Holy Spirit, we would never want to return to the darkness of our former lives.
If the Roman believers had clung to the sins they left behind to follow Christ they would still be on the path to eternal death, storing up wrath for themselves on the day of judgment (2:5). With this reminder of the outcome of enslavement to sin, Paul motivates his readers to persevere along the path of righteousness, which yields the fruit of holiness and, ultimately, eternal life.