The question at this point is: why is circumcision (or anything we do) unable to make us right with God (Galatians 5:6; cf. 3:10, 21)? Just as the wages we earn have nothing to do with being a gift we receive, so circumcision or anything we do can have nothing to do with making us right before God, because righteousness is imputed (i.e. it is a gift), and what we do looks for a wage (reward for services rendered). It is Christ who makes us righteous (through grace, a gift), and we can only trust it is so, just as we trust that any gift we receive is entirely a gift—no strings attached.
The operating principle of our faith is love. Simply believing something is not effectual. Faith operates through love. Unless I live as Christ lived, there is no evidence of Christ’s Spirit operating within me. I trust Christ, if I let his Spirit work in me causing me to desire and do those things Christ did. When asked what works we could do in order to do the work of God, Jesus replied that folks need to believe on him whom God sent (John 6:28-29). Trusting in Jesus implies receiving him as Lord or as one’s authority. We express our faith in him by living in his name, doing things similar to what he did—loving and helping others. Yet, living in his name and doing as he did does not come from the flesh but through the Spirit within us, as Paul claims in Philippians 2:12-13.
The Judaizers tripped the Galatians up in their walk with Christ. The image Paul gives us in Galatians 5:7 is that of runner running a race and someone bumps or trips the runner, causing him to fall. The Galatians were running well; they were doing the right things. It seems that those, who are sincere believers and conscious of a desire to please God, are more susceptible to the pressure of a legalist than are casual believers in Christ. This is why such a doctrine is so dangerous and destructive, because it takes one’s eyes off Christ and puts them on man.
What Paul wants believers to realize is, the doctrine of the Judaizers is not the Gospel (Galatians 5:7-8; cf. 1:6-7; 3:1-2). These people were not sent by God to preach their doctrine, and obeying them causes one to be disobedient to God, who commands us to trust Christ. Paul cannot be tolerant under such circumstances (Galatians 5:9), because even a little compromise to the authority of the Law poisons the whole idea of complete trust in Christ. One cannot be partially trusting Christ—it must be complete for Christ to be effective in our lives.
Paul is confident on two points. First, he is confident that the Lord will cause the Galatians to agree with Paul’s defense of the Gospel. Secondly, Paul is confident in the Lord that he will judge the works of those who sought to undermine his Gospel (Galatians 5:10). They had slandered Paul, claiming that he preached circumcision, but Paul asked the Galatians, if that were true, why was he still persecuted by those who embraced the Law (Galatians 5:11)? The argument of the Judaizers is simply illogical.
The message Paul preached was Christ crucified (Galatians 5:11b). This is an offense to both Jews and Greeks. To the Jew it was a stumbling block—how could their Messiah die under the curse of God? To the Greek it was foolishness—how could someone who was executed save anyone? He couldn’t save himself! To those who believe, however, Christ is the wisdom of God (because the foolishness of God – preaching – is wiser than men; and the weakness of God – Christ crucified – is more powerful than men (1Corinthians 1:21-25).
Today, Christ becomes a stumbling block to modern Christians who believe Christ alone is not enough for their salvation. When we believe we cannot be saved unless we do this or that, we cease to trust in the only means of salvation that God has offered us. It is Christ alone or we are on our own.
In Galatians 5:12 the image is that of circumcision. Paul likens the legalist to the flesh that is cut off from the body of men. He would prefer that they cut themselves off from the Body of Christ, because they have nothing to do with the righteousness of Christ. Paul expresses such anger and intolerance, because these people aren’t merely preaching something that could be true—that some within the Body of Christ believe might be true. They are preaching something that cannot be true. To accept their doctrine is to reject the Spirit of Christ working in us for our sanctification.