Galatians 2:11

But when Cephas came to Antioch, I resisted him to the face, because he stood condemned. [There is no means of determining when this scene took place, but it was probably very soon after the council at Jerusalem. It forms the climax in Paul's argument, showing that he was not only the equal of Peter, but, at times, even his superior. It upsets the Romish doctrine of Peter's supremacy, and also shows that in his conduct he was not infallible; for in this instance he was not so much condemned by his fellow-apostle as he was, to use Paul's phrase, self-condemned--his conduct at one time reproving and convicting him for his conduct at another. Luther regards Paul as here drawing a contrast between his own conduct in withstanding Peter to his face, and these gospel perverters who were slandering him behind his back.]