Verse 13: And the other Jews dissembled likewise with him; insomuch that Barnabas also was carried away with their dissimulation. This means that Peter had other Jews who followed him in his hypocrisy. The NASB translates the verse, And the rest of the Jews joined him in hypocrisy, with the result that even Barnabas was carried away by their hypocrisy.
Make no mistake, people are always watching us. Nothing is more destructive than hypocrisy. On that note, I would rather see a young person attend a blatantly heathen university than one that pretends to be Christian. Why? - Because it is always easier to fight when you know who your enemy is.
Verse 14: But when I saw that they were not straightforward about the truth of the gospel, I said to Cephas in the presence of all, "If you, being a Jew, live like the Gentiles and not like the Jews, how is it that you compel the Gentiles to live like Jews? The truth of the gospel was freedom from the Law. At issue here is that by their actions, they were trying to impose Law and kingdom teachings on the Gentile grace believers. Think about it, if the Jews lived like Gentiles, why would they tell Gentiles to live like them? Again, if they cannot live as Jews under the law, why would they tell others to do it?
The same can be said of the church today. If we live like the world, why tell them to live like the church? Sadly, the church has become so relevant that it has become irrelevant on many levels. Most people are not opposed to God, just the church who is supposed to be representing Him.
Verses 15-16: We who are Jews by nature, and not sinners of the Gentiles, Knowing that a man is not justified by the works of the law, but by the faith of Jesus Christ, even we have believed in Jesus Christ, that we might be justified by the faith of Christ, and not by the works of the law: for by the works of the law shall no flesh be justified. The phrase we are Jews by nature simply refers to those who were born Jews including Paul. As for the rest of we are the sinners from among the Gentiles. However, please understand that Paul is not saying that the Jews are not sinners as well. He said as much in Romans 3:23 when he said that all have sinned and come short of the glory of God.
It also must be understood that Paul here is not addressing all Jews but only those who know that a man is not justified by the works of the law, but by the faith of Jesus Christ. So the language makes it clear that he is addressing those Jews who had placed their faith in Christ and not the law. This would mean that they are grace believers.
Again, he says that by the works of the law shall no flesh by justified. This has to be referring to the new dispensation of grace because under the old dispensation of law they were justified by the works of the law. Paul said in Romans 2:13, For not the hearers of the law are just before God, but the doers of the law shall be justified. This verse is clearly not referring to this present dispensation of grace. Also, James 2:20-26 also says the exact opposite when he said, But wilt thou know, O vain man, that faith without works is dead? Was not Abraham our father justified by works, when he had offered Isaac his son upon the altar? Seest thou how faith wrought with his works, and by works was faith made perfect? And the scripture was fulfilled which saith, Abraham believed God, and it was imputed unto him for righteousness: and he was called the Friend of God. Ye see then how that by works a man is justified, and not by faith only. Likewise also was not Rahab the harlot justified by works, when she had received the messengers, and had sent them out another way? For as the body without the spirit is dead, so faith without works is dead also. Why the seeming contradiction between the two? Different audiences. Paul was the apostle to the Gentiles and James was writing to the Jews who were still under the law. Sadly, most today mix the two and cause tremendous amounts of confusion to the Body of Christ.