Grace I

2 Peter 3:15-16 And account that the longsuffering of our Lord is salvation; even as our beloved brother Paul also according to the wisdom given unto him hath written unto you; As also in all his epistles, speaking in them of these things; in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction.

Paul had received a divine revelation about the gospel of the grace of God, which was not revealed to the first apostles. This was acknowledged by all, including Peter. 

In Galatians 2, Paul rebuked Peter publicly at Antioch for not acting in a manner worthy of the gospel he preached. Peter was a great pillar of the New Testament church. For Paul to openly rebuke him means Paul knew exactly what he was doing. For Peter to accept the rebuke is a sign that he recognised what was on Paul. Peter's actions were hypocritical. At one point, he sided with those of the uncircumcision, signifying that God had accepted them by grace into the body of Christ. Then, at another instance, he distanced himself from any contact with them when those of the circumcision arrived. That did not go well with Peter, and he went ahead to rebuke him! In all that, Paul's point was simple: all are saved by grace through faith, whether they are circumcised or not, so we should not be ashamed of associating with them as brethren.  

Are you preaching the same gospel that Paul preached? The true gospel is the Word of His grace, the message that brings salvation, hallelujah.

Further scriptures

Gal 2:11-12 ‘But when Peter was come to Antioch, I withstood him to the face, because he was to be blamed. For before that, certain men came from James, he did eat with the Gentiles: but when they were come, he withdrew and separated himself, fearing them which were of the circumcision.’