Charles Ellicott Commentary Romans 6:15

"What then? shall we sin, because we are not under law, but under grace? God forbid." — Romans 6:15 (ASV)

The Apostle returns to a difficulty very similar to that which presented itself at the beginning of the chapter. The answer is expressed through a slightly different metaphor. It is no longer death to the one, life to the other; but freedom from the one, service to the other. These are correlative terms. Freedom from sin implies service to God, just as freedom from God means service to sin. The same idea of service and freedom will be found worked out in John 8:32-34, John 8:36, and Galatians 5:1.

On verses 15-23:

Free forgiveness! What does that mean? Freedom to sin? Far from it. That would be to return to the old slavery. To yield to sin is to be the servant or slave of sin, with its consequence—death.

On the other hand, obedience and righteousness go together. Happily, you have escaped from sin and become servants to righteousness. Service, I say, using a plain human figure to suit your imperfect and carnal understanding of spiritual things. Exchange the service of uncleanness for that of righteousness.

I appeal to your own experience. You found that sin brought you no pay from your master except death. Now you have started on a road that leads to sanctification and eternal life. This will be given to you, not as wages, but as the free gift of God in Christ.