The Christian faith is often likened to a marathon. The Galatians started off well when they first heard the gospel, and had every possibility of reaching the goal. But now someone has tripped them, so Paul asks: Who distracted you (Galatians 5:7)? The Judaizers obviously, and they are pushing their agenda. But Paul points out that adopting circumcision is disobeying the truth of the gospel; it is stepping off course, which means instant disqualification. He exhorts them to pull back before it's too late.
But when it comes to salvation, even a tiny deviation can result in total ruin, just like the effect of a little yeast in a batch of dough.
The Galatians tripped up perhaps because Paul's opponents are attractive, eloquent, and persuasive speakers, who attempt to sway them to their cause (v. 8). But Paul identifies the source of their persuasion: not God, and thus by implication the devil. Moreover, God calls us to salvation based on the truth He revealed, not some clever human argument, however persuasive it might be.
Paul uses what is probably a proverbial saying to drive home his point (v. 9). The Judaizers are not seeking to overthrow the Galatians' entire belief system. They just want to add a little something more. But when it comes to salvation, even a tiny deviation can result in total ruin, just like the effect of a little yeast in a batch of dough. Paul warns the Galatians: you've already begun observing special occasions (4:10), if you tolerate the Judaizers' insidious heresy further, all will be ruined.
A rumour must be making its rounds which the Judaizers are exploiting in full: that Paul himself sanctions circumcision (5:11). ″Remember Timothy?″ they might have asked (see Acts 16:3). Not true, Paul retorts. He has preached nothing except the cross-the symbol of God's justification of sinners through faith in His Son, Jesus the Messiah. But the Judaizers find a cursed and dying Messiah, and God's justification without human effort, offensive. ″That's why they persecuted me″, Paul says. Moreover, he would be agreeing with the Judaizers if the rumour were true. In that case, ″the offence of the cross″ (Galatians 5:11) would be removed, and salvation through faith in Christ alone would be nullified. What a silly allegation!
Paul reserves his harshest words for his critics. If circumcision is so important, why not go all the way and be castrated like the pagan priests (v. 12)? Is he angry? Perhaps, but it is more than just taking personal offence; at stake here is the truth of the gospel and the preservation of Christ's church. Paul shows us the importance of tracing the source of all teachings. If they are not from God, we must ignore them, otherwise we can easily be bumped off course.