It is wrong, therefore, to pit grace against law in the process of sanctification. Of course, there are right an wrong ways of expressing the relationship between them. But we should reject the notion that we should live only according to the gospel and not according to the law. All our goodness is by grace. But the gracious work of the Spirit enables us to keep “the righteous requirement of the law” (Romans 8:4).
It would be equally wrong, however, to imagine that once we have trusted Christ for salvation we may then forget about the gospel and go about trying to obey the law. It is important, not only to obey the law, but obey it for the right reasons, which include the grace given in the gospel. We can never forget what Jesus has done for us, and his great work changes the way we look at God’s law.
We have seen that justification and sanctification are different. In justification, our works play no role. God accepts us as righteous solely on the basis of Christ’s atonement. In sanctification, God’s grace is equally pervasive, but there is a role for our efforts. All our goodness comes from God, but it is still important for us to take up arms against Satan and do what is right.
So Protestants have maintained that justification is “by faith alone.” Sanctification is also by faith, but not by faith alone. It is important to emphasize both parts of this statement about sanctification. It is not by faith alone, for human effort is necessay to achieve it. Of course, it is God’s grace that gives us the ability to put in that effort. But human effort is necessary for sanctification in a way that it is not necessary for justification.
Even though sanctification is not by faith alone, it is certainly by faith. In our quest for holiness, we must reckon ourselves dead to sin and alive to God. We must remember that because of Christ we are the people of God, son and daughters of God, friends of God, the bride and body of Christ, and the temple of his Spirit. In other words, we must remember the gospel.
~ John Frame in The Doctrine of the Christian Life, pp. 915-916.