This chapter and the next two emphasize how we successfully live as followers of Jesus after we have trusted him. As he did in chapter 3, Paul repeats that God’s grace should not be used as an excuse to continue sinning. He reminds us that when we trusted Jesus, our old self died and a new one came into being. The old one was the unwilling slave of sin. The new one should be the willing slave of God. Paul cannot understand a person wanting to return to that old way of life.
The old way of living can look pretty tempting sometimes. People who live like that sure seem to be having fun. Maybe it’s only tempting to sin a little bit. Our former slavery to sin still has a hold on us. We need to constantly remind ourselves that we came to Christ because we recognized how bad our sin was. Why would we go back to what we at one time recognized was self-destructive?