Romans 6:15–16—A warning about grace as an excuse for any sin.

These verses introduce the theme of the chapter’s last section. Just as to be “under law” is to be subject to law’s demands, life “under grace” brings its own set of obligations. Christians are not free to live as we want, but we are still slaves, no longer of sin but now of righteousness (verse 18). Or, as Paul puts it in Galatians 6:2, we obey the law of Christ.

Distinct questions, different issues
The question in verse 15 seems to repeat the question in verse 1, but they differ in two respects. First, the verb tenses vary. The present tense in verse 1 (“Are we to continue in sin that grace may abound?”) changes to aorist in verse 15. This tense suggests a particular occurrence, which shifts the issue from a lifestyle of sin to occasional acts of sin. “Are we to commit a sin?” he now asks.

What Paul is getting at, according to Bob Utley, is “the Christian’s need to fight, or resist, individual acts of sin.” As A. T. Robertson says, Paul is confronting the idea that “we may take a night off now and then and sin a little bit ‘since we are under grace’.” Occasional sins easily become habitual, and Paul’s return to present-tense verbs in verse 16 suggests he is warning believers against reverting to a sinful lifestyle, which would make us once again slaves to sin.

The second difference between the two questions is that they look at grace from different perspectives. Douglas Moo explains the variation: “in 6:1 it is a question of sinning in order to gain more grace, while in 6:15 it is a question of sinning because of grace” (his emphasis). Of course, Paul’s answer to both questions is a resounding “By no means!” His purpose in asking them is to explore the dual, overlapping accomplishments of grace in sanctification, and of course to explain how we must live in the age of grace.

God’s work and our responsibility
Verse 1 opened Paul’s discussion of what grace has already accomplished for us through our union with Christ in death and resurrection, as his followup question makes clear: “How can we who died to sin still live in it?” The point of that question, then, is the foolishness of seeking to gain more grace by sinning when grace has already overcome the power of sin.

Verse 15 shifts the attention from what God has done for us to our responsibility to obey him. To sin because we are not under law but under grace is to misunderstand both law and grace. As Paul has forcefully argued, people are misguided if they think law functions well as a restraining influence on sin. The far more powerful constraint on sin is grace, because it imparts the ability to obey.

An analogy
A classroom of sixth graders find out that they are getting a new teacher. Mr. Law, a stern taskmaster, is being replaced by Miss Grace. Thinking she will be a pushover, the students plot all kinds of mischief, but they are in for a surprise. Miss Grace turns out to be so beautiful, caring, and competent that the students’ attitudes change. Now wanting to please her, they even work harder in the classroom and on homework with the result that their progress and grades improve.

If only classroom management were as simple as this illustration! But supernatural grace does effectively do what this analogy suggests. Grace plants the desire to obey God in our heart (see verse 17 and 8:2–6) and empowers us by the Holy Spirit to live out that desire (Galatians 5:16–18). The beauty of grace is to make us beautiful. It does this, in part, by equipping us to obey.

“If you present”
Paul addresses the rhetorical question in verse 16 to Christians as he continues to speak about sanctification, not salvation. Whereas unbelievers are by default slaves to sin and can only choose the kind of sin they wish to obey, believers are free to choose between sin and righteousness.

The Roman believers, some of whom were slaves or former slaves, knew very well the maxim that people are slaves of whichever master they obey. They were aware as well that slaves are under the total control of their masters. That is the meaning of the term slave in this chapter (the Greek word is doulos, sometimes translated servant or bondservant). If we obey sin, we again become slaves of the sin from which Christ set us free.