Some people think that they can make it to heaven on the basis of their good works. Is this really true? That's the question Paul deals with: How can a sinner be justified before God on judgment day? Can we count on our own efforts, and if not, what can we count on?
By adding human effort (law keeping), we no longer solely rely on God's gracious provision in Christ for our salvation; for by submitting to it, we are putting confidence in human effort.
Paul has previously stated that it is futile to seek justification through works of the law (Galatians 3:10). Now he adds that it is not only futile, but actually fatal. He issues a stark warning: submission to the law through circumcision will instantly and completely separate us from Christ (5:4). In fact, we will be taking ourselves out of the domain where His grace operates. By adding human effort (law keeping), we no longer solely rely on God's gracious provision in Christ for our salvation; for by submitting to it, we are putting confidence in human effort. As John Calvin observes: ″Whoever wants to have a half-Christ loses the whole″.4
But those of us, Paul continues, who rely solely on faith in Christ can eagerly look forward to that day when God will justify us before everyone (v. 5). We might be justified now through Christ, but the rest of the world neither knows nor acknowledges it. But there will come a day when all who are in Christ shall be revealed and declared righteous by God before the entire universe. No one will be able to dispute the fact or contest the verdict. This hope is kept alive in us always by the power of the indwelling Spirit; it is an assured hope and hence will not put us to shame (Romans 5:5).
In contrast, the law cannot assure us. Those who rely on it (or any human effort) can only ″hope″ that they will receive a favourable verdict from God on that day. Not so with those who look only to Christ; we already have the Spirit's assurance what the outcome will be.
In God's eyes, Paul tells the Galatians, circumcision (rules, or human effort) really amounts to nothing; the only thing that matters is faith (Galatians 5:6). ″For in Christ″-that is, within His sphere of operation-circumcision or un-circumcision is irrelevant (v. 6). It may have been important in the past, but not anymore. So why hang on to it? Paul's message to the Galatians and to us today is: concentrate purely on Christ!
So how can guilty sinners be justified by God on the last day? Through faith in Christ, not by works of the law or human effort. If we look to Christ only, our hope on the last day will be assured.