Albert Barnes Commentary Galatians 2:21

"I do not make void the grace of God: for if righteousness is through the law, then Christ died for nought." — Galatians 2:21 (ASV)

I do not frustrate the grace of God. The word rendered "frustrate," atheto, means, properly, to displace, abrogate, or abolish; then to make void, or to render null (Mark 7:9; Luke 7:30; 1 Corinthians 1:19).

The phrase "the grace of God" here refers to the favor of God manifested in the plan of salvation by the gospel, and is another name for the gospel. The sense is that Paul would not take any measures, or pursue any course, that would render that vain or ineffective.

Neither by his own life—that is, by a course of conduct which would show that the gospel had no influence over his heart and conduct—nor by the observance of Jewish rites and customs, would he do anything to render that ineffective. The design is to show that he regarded it as a great principle that the gospel was effective in renewing and saving people, and he would do nothing that would tend to prevent that impression on humankind.

A life of sin, of open depravity and licentiousness, would do that. And, in like manner, a conformity to the rites of Moses, as a ground of justification, would tend to frustrate the grace of God, or to render the method of salvation solely by the Redeemer futile. This is to be regarded, therefore, as both a reproof of Peter for complying with customs that tended to frustrate the gospel's plan, and a declaration that Paul intended his own course of life to confirm the plan and show its effectiveness in pardoning the sinner and making him alive in God's service.

For if righteousness come by the law . If justification can be secured by the observance of any law—ceremonial or moral—then there was no need for the death of Christ as an atonement. This is plain. If people by conformity to any law could be justified before God, what need was there for an atonement?

The work would then have been wholly in their own power, and the merit would have been theirs. It follows from this that people cannot be justified by their own morality, or their charitable deeds, or their forms of religion, or their honesty and integrity. If they can, they need no Saviour—they can save themselves.

It follows, also, that when people depend on their own good nature, morality, and good works, they will feel no need of a Saviour; and this is the true reason why most people reject the Lord Jesus. They suppose they do not deserve to be sent to hell.

They have no deep sense of guilt. They confide in their own integrity and feel that God ought to save them. Hence they feel no need of a Saviour; for why should a healthy person employ a physician? And confiding in their own righteousness, they reject the grace of God and despise the plan of justification through the Redeemer.

To feel the need of a Saviour, it is necessary to feel that we are lost and ruined sinners, that we have no merit on which we can rely, and that we are entirely dependent on the mercy of God for salvation. Thus feeling, we will receive the salvation of the gospel with thankfulness and joy, and show that in regard to us Christ is not dead in vain.