If Christ’s sacrifice completely paid the penalty for all my sins past, present, and future, why do I need to adhere to God’s commands? If it’s all been forgiven already, why can’t I do whatever I want?

Those questions, in one form or another, have puzzled believers going all the way back to the earliest days of the church. In fact, Paul, under the inspiration of the Holy Spirit, dealt with that very issue in his letter to the Romans. “What then? Shall we sin because we are not under law but under grace? May it never be!” (Romans 6:15).

In our current blog series, we’re looking at the intersection of sin, grace, and righteousness in the life of the believer. And the role of God’s law is fundamental, both for understanding the true nature of our sin, and setting the course for righteous, godly living.

So what is the role of the law for believers? There is a great divide in the church as to how to answer that question. On one side you’ll find people who de-emphasize the law’s importance by stressing the value of God’s grace and the righteousness of Christ that is applied to our eternal account. But that perspective risks undermining the importance of sanctification, and makes the standard of God’s law an afterthought.

On the other side, you’ll find legalists who overemphasize the law, and even add to it. Their fastidious adherence to a list of rules is meant to be a display of their godliness and spiritual maturity. But often, legalism is nothing more than behavior modification. It doesn’t promote spiritual growth or maturity—it turns people into Pharisees.

So then what is the answer? How does the law function in the believer’s life? We recently asked John MacArthur to help us make sense of this highly practical and deeply theological issue. Here’s what he said:

As Paul wrote in Romans,

But thanks be to God that though you were slaves of sin, you became obedient from the heart to that form of teaching to which you were committed, and having been freed from sin, you became slaves of righteousness. (Romans 6:17-18)

In the coming days we’re going to take a closer look at what it means to be a slave of righteousness, and the believer’s new nature in Christ that enables him to adhere to God’s law.