Twice in Galatians 2 Paul speaks of โthe truth of the gospel.โ In both cases the Apostle had been forced to speak out to defend the purity of โthe gospel of the grace of Godโ (Acts 20:24).
In Gal. 2:4,5 he refers to his contest with those at Jerusalem who would have brought the Gentile believers under the law of Moses. Among them were โfalse brethren,โ he says, โunawares brought inโฆ to spy out our liberty which we have in Christ Jesus, that they might bring us into bondage: to whom we gave place by subjection, no, not for an hour, that the truth of the gospel might continue with you.โ
In the second case he refers to a controversy with Peter who, having enjoyed blessed fellowship with Gentile Christians, had been intimidated by some of his Jewish brethren into separating himself from the Gentiles. Concerning this, Paul writes: โBut when Peter was come to Antioch, I withstood him to the face, because he was to be blamedโ (Gal. 2:11). Why was Peter to be blamed? Gal. 2:14 answers: Because he โwalked not uprightly according to the truth of the gospel,โ i.e., โthe gospel of the grace of God,โ in which believing Jews and Gentiles are โone body in Christ.โ
How we should all thank God for Paulโs vigorous defense of the gospel of grace, under which all who trust in Christ as Savior are baptized by the Holy Spirit into the one true Bible Church (I Cor.ย 12:13).
Doubtless Paulโs stand for โthe gospel of the grace of Godโ stemmed from the fact that he himself had experienced the truth of this blessed message. As the chief of sinners he had been gloriously saved. All his power and prestige as a Pharisee, all his intellectual achievement, all his rigid Law observance meant nothing now, as in the presence of the glorified Lord he saw himself a sinner, the chief of sinners, and was saved by the matchless grace of God. source