What then? Shall we sin because we are not under law but under grace? By no means! Don’t you know that when you offer yourselves to someone to obey him as slaves, you are slaves to the one whom you obey—whether you are slaves to sin, which leads to death, or to obedience, which leads to righteousness? But thanks be to God that, though you used to be slaves to sin, you wholeheartedly obeyed the form of teaching to which you were entrusted. You have been set free from sin and have become slaves to righteousness.
Paul equates the law with sin as the law constantly points out our sin. Likewise the law causes us to sin in that it creates a standard which we constantly fall short of.
Because we all fall short of the law, we need grace to wash away our sin. The Romans thought that more sin brought about more grace and hence it was a good thing. Paul says just the opposite.
Even though salvation isn’t found in obeying the law, we are still called to obedience. We will always serve a master of sin or righteousness, doing what one or the other wants us to do.
There is a stark difference between obeying God and following the law. Even though the end result may appear to be the same because the rules are the same, the result is drastically different.
Obedience to God is done out of love. We obey because we love God and want to please Him. Because of this, obedience is a joy, not a drudgery. Following the law is done out of duty however. We follow the law because we feel that we must because we expect a reward or fear the punishment for not following.
Following out of duty will produce a poor follower because we are incapable of following perfectly. Obeying God comes easily because God knows that we aren’t perfect and we know that we’ll experience forgiveness when we fall short.