"I am astonished that you are so quickly deserting the one who called you to live in the grace of Christ and are turning to a different gospel." (Galatians 1:6)
Galatians is the most urgent of Paul's letters, written in anger and grief to communities in the Roman province of Galatia that he had founded and that are now being seduced by teachers who insist that Gentile converts must be circumcised and observe the Mosaic Law to be fully saved. Paul does not begin with his usual thanksgiving. He goes straight to the crisis: I am astonished that you are so quickly deserting the one who called you to live in the grace of Christ and are turning to a different gospel. The desertion is not from Paul but from God. The different gospel is not really a gospel at all. And if anyone, even an angel from heaven, preaches a gospel other than the one Paul preached, let them be under God's curse. He says it twice, for emphasis.
Paul then defends the divine origin of his Gospel: he did not receive it from any human source, nor was he taught it. He received it by revelation from Jesus Christ. He recounts his pre-Christian past as a persecutor of the Church and his conversion, after which he did not consult with any human being, did not go up to Jerusalem to see the apostles, but went into Arabia and returned to Damascus. It was three years before he went to Jerusalem to meet Peter, staying fifteen days. His Gospel was not derived from the apostles in Jerusalem; it came independently from the same risen Christ who appeared to them.
Brothers and sisters, Paul's astonishment at the Galatians' desertion is a measure of how quickly the Gospel can be distorted when additional requirements are attached to grace. Every generation of Christians faces its own version of the Galatian error: the subtle addition of conditions to the free gift, the suggestion that grace alone is not quite enough. Test every teaching you receive against the original Gospel: salvation by grace through faith in Christ alone. If anything is added as a requirement for full standing before God, the curse of Galatians 1 applies.
Lord God, guard us from every distortion of the Gospel that adds human conditions to your free grace. Let the revelation you gave Paul be the revelation that governs our faith: not another gospel, not an improved gospel, but the one Gospel of Jesus Christ crucified and risen. Through Christ our Lord. Amen.