In Galatians 2, Paul begins shifting his focus from proof that he was not a "grade-B" apostle, to proof that Christians do not need to keep the Old Testament law -- whether for justification or sanctification! This is a message that every law-keeper -- whether Catholic, Adventist, Mormon, or Jehovah's Witness -- needs to heed.
14 years after he first visited Peter and James, Paul returned to Jerusalem with his colleague Titus. Evidently this meeting was necessitated by false reports about Paul spread by Jewish cultists who had slipped into the Jerusalem church posing as Christians (2:4). The Lord told Paul to go ("by revelation", 2:2). Paul sat down privately with James, Peter, and John (who seemed to function as the overseeing triumvirate among the original twelve apostles), and they discussed his ministry and message with him. I can imagine these conversations were lengthy, intense, and went well into the night.
How did it all turn out? For one thing, the apostles did not insist that Titus be circumcised, even though he was right there and he was a Gentile (2:3). Second, Peter, James, and John did not correct or amend anything in Paul's doctrine. They added nothing to him (2:6). Third, they saw Peter and Paul as equal apostles, recipients of the same grace, just with different commissions to different groups (2:7-8). Last, the three endorse4d Paul's message and ministry by giving him the right hand of fellowship, which was a public affirmation of Paul and his work (2:9).
Circumcision was the premiere ceremonial mark of the Law. It was one of the two physical symbols of God's covenant with Abraham (Genesis 17:9-14), the other being the Sabbath. It added a legal and national factor to Abraham's covenant. Circumcision symbolized being under the legal authority of the Lord God Almighty, and for that reason it included non-Jewish slaves (Genesis 17:13). To dispense with circumcision was to dispense with Old Covenant Law altogether.
Christians are not under the Old Covenant Law at all. By not requiring Titus to be circumcised, the apostles were saying that being a member of God's family is different from being an Israelite. The Christian Church is not Israel. It is bigger than Israel. We are a movement, not a bloodline. We are a faith, not a clan. By standing firm against the idea that Christians should come into bondage to the Old Covenant law, Paul kept Christianity an international faith.