The problem lies in the transgression of the law—sin—rather than the law itself. "Sin, that it might appear sin" refers to the function of the law: It reveals what sin is. "What is good" is the law or the commandment itself (see verse 12).
John W. Ritenbaugh
The Covenants, Grace, and Law (Part Twenty-Seven)
Notice that it was not the law that killed him but sin! Plain, simple truth—sin slew him. By contrast, Paul says that the law was ordained to life. It is holy, just, good, and spiritual. That is very clear.
John W. Ritenbaugh
The Covenants, Grace, and Law (Part Twenty-Nine)
Do we not believe that Paul was a sincere and dedicated example of a fully committed Christian? Yet, his testimony confirms that we have to face and accept the humbling fact that sin, as long as we are in the flesh, forever stains our character. We will never be rid of it until our change in the resurrection. Can we accept the fact that no amount of personal exertion to purge ourselves of sin will be completely effective? Paul did, and it led him to be thoroughly humbled and thankfully aware of God's mercy.
However, it did not cause him to disregard whether he sinned. Paul resolved not to sin because he loved Christ for what He had already done and continued to do every day. As a former Pharisee, he understood that super-righteousness (Ecclesiastes 7:16) on his part would never work.
In I Corinthians 15:8-10, he makes a telling statement about how he judged his past before his conversion:
Then last of all He was seen by me also, as by one born out of due time. For I am the least of the apostles, who am not worthy to be called an apostle, because I persecuted the church of God. But by the grace of God I am what I am, and His grace toward me was not in vain; but I labored more abundantly than they all, yet not I, but the grace of God which was with me.
Paul had a firm understanding that super-righteousness could not replace what Christ had already mercifully done in his behalf, and nothing he did could ever replace it. He used this as an example, as a prod to himself, so he would never forget exactly where he stood in terms of being gifted by God's grace. It took a perfect Sacrifice to pay for his past sins and also those he continued to commit as a Christian! Despite sin still being a part of him, he says, “I am what I am by means of God's grace.” He valued what was done on his behalf so deeply that he never let his appreciation lag.
He adds in Romans 4:4-8
Now to him who works, the wages are not counted as grace but as debt. But to him who does not work but believes on Him who justifies the ungodly, his faith is accounted for righteousness, just as David also describes the blessedness of the man to whom God imputes righteousness apart from works:
Blessed are those whose lawless deeds are forgiven,
And whose sins are covered;
Blessed is the man to whom the LORD shall not impute sin.
Do we truly understand that we cannot add to the quality of the righteousness of Jesus Christ, the Son of God, who lived without sinning His entire life? When His pure righteousness is accounted to us, we stand before God blameless because of His sinlessness. Even our righteousness done through our obedience following baptism and receipt of God's Holy Spirit lacks the purity of Christ's righteousness imparted and accounted to us, because our righteousness is still tainted by sin that remains within us.
I Corinthians 1:26-31 contains a truth of supreme importance to us: God called the weak and base of the world, and no flesh will ever glory in His presence. This is why our integrity must be guarded by humility because our obedience—given because of God's mercy and which He graciously accepts—is still flawed.
None of this removes our responsibilities regarding our continuing sanctification; it does not do away with our accountability to obey God's law and grow in the grace and the knowledge of Jesus Christ. We do not stop learning, obeying more perfectly, and maturing within the relationship that we now have with the Father and Son. Nevertheless, we cannot add to the righteousness of Christ. It is futile even to think such a thing—and that is why it is dangerous.
Upon receiving God's Spirit, attitude is of major importance. Conversion is a matter of a changed heart combined with more perfect knowledge of His truth. It is a matter of knowing, believing, living in, and accepting our place within the relationship. It is a matter of submitting with all our heart to the Father's placement of us within the body. A person with wisdom will know he must not go beyond what the relationship will permit.
John W. Ritenbaugh
Ecclesiastes and Christian Living (Part Eleven): Paradox, Continued
Other Forerunner Commentary entries containing Romans 7:13: