Galatians 2:14

But when I saw that they walked not uprightly according to the truth of the gospel, I said unto Cephas before them all, If thou, being a Jew, livest as do the Gentiles, and not as do the Jews, how compellest thou the Gentiles to live as do the Jews?

I said unto Cephas ... before them all ... This bold rebuke administered by Paul to Peter may not be taken as a relaxation of Jesus' rule that the brother having sinned should first be approached privately (see my Commentary on Matthew, Matthew 5:24). The situation was not one which pertains to any persons today, for both Paul and Peter were inspired apostles of the highest rank; and the near-unique situation demanded exactly what Paul did here. We therefore disagree with Hendriksen that here is established the principle of "rebuking publicly those who have sinned publicly,"[27] unless and until the three steps commanded by Jesus in Matthew 18:15-17 have been taken. Church leaders, as recommended by Calvin, taking upon them to imitate Paul's action here, are presuming far too much. Besides, it is not certainly known that Paul had not already, in this case, taken the steps of the first and second admonitions, as he had instructed Titus to do (3:10); but no matter what Paul did, it is the instruction to Titus that more correctly fits the analogy with church leaders today. See much more on this in my Commentary on Matthew, Matthew 18:15.