He reminds them he had basically no interaction with any other apostles and was not influenced by their message... the message he was sharing was from God alone.
14 years after Paul first met James and Peter, he went again to Jerusalem, meaning he had preached the same message for 17 years now, without any previous instruction. He told that a message from God alone, received directly from Jesus himself. Paul here is talking here about the Council of Jerusalem that occurred in Acts 15 in AD 50. What was the purpose of that visit and of the Jerusalem Council? To address the current controversy, to address what is required of non-Jewish/Gentile believers. Specifically, he discusses that Gentiles do not have to do extra things to make God happy.
Why did Paul mention Titus? Remember, Paul wrote a letter to Titus (Titus 1:4-5). But why did he mention him? Because Paul had led him to Christ and Titus was an uncircumcised Gentile Christian, which was the very thing the controversy was about. He wanted to show them a real life example of such a believer and that even without doing all the extra things the Jewish self-righteous and legalistic believers expected of him, Titus was clearly godly. His point is that there are Christians who don’t look like you, live completely like you, dress like you, have different cultures than you and express their faith differently than you– but they love Jesus JUST AS MUCH.
In Acts 15:1, Paul mentions Judaizers who came to Antioch, which is in Pisidia or Galatia. These Jewish Christians were coming at that time, teaching that you had to be circumcised in order to be a Christian in good standing with God. Then, at that Council in Jerusalem, after Paul told them what God had done among non-Jewish believers, this group of Judaizers still said (Acts 15:4-5) that it was necessary to circumcise them. Paul said no. We shouldn’t place too much emphasis on externals; even without those things, Titus was actually MORE RIGHTEOUS than these Galatians. So when the Judaizers were confronted with the truth about their legalistic perversions of the gospel, they ‘kept silent.’
In verses 3-5, Paul discusses false brethren who taught that circumcision is necessary. They tried to spy out our freedom, to put us back in religious bondage (religious tyranny), making us and others do more than God required. But, Paul said, we didn’t yield in subjection to them for even an hour. We only cared about the truth. When it comes to impressing people with being overly strict and proving to them that you’re the real thing and accommodating them and their self-righteous, extra-biblical demands on your life– Paul said he wouldn’t deal with it.
That’s why Paul calls them ‘false brethren;’ they knew nothing of the grace of God, they were just religious zealots wanting to control people’s lives for their own power. Those phonies and power mongers had sneaked into the leadership— Paul here is using a type of military language, where people enter a camp by stealth with an objective of sabotage— and they wanted to bring people into bondage (the same word that implies ‘slavery’).
Paul’s point is that these people were more interested in controlling people and performing self-righteous acts to earn favor from God and praise from one another MORE THAN realizing God gives His favor as unmerited and free, without performance. MEANING, anything we do for God should be out of love and devotion for God, not to impress or control others or to gain the praise of other people.
Paul enforces his point through a variety of methods and supports. In doctrinal issues (beliefs), Paul changed nothing– as it says here. He wouldn’t change his beliefs to make them palatable to people, Christian or not. But in ministry matters– to reach people for Christ, he was always being unconventional; 1 Corinthians 9:22 says I ‘became all things to all men, that I might by all means save some.”
Example: Though Paul didn’t have Titus circumcised (a Gentile) he did have Timothy circumcised. Why? Titus wasn’t circumcised because Titus was a Grecian Gentile and had no relationship to Judaism. But because Timothy was half-Jew, without being circumcised, Timothy couldn’t have gone into the synagogue to preach and minister to Jews. Titus, the Greek, had no inroads to the Jews, but Timothy did– but for ministry reasons, not theological reasons, Paul wanted Timothy to be circumcised...not for self-righteous reasons, but because it allowed him to be more effective in ministry with his people.
In closing, Paul said in verses 2:9-10 that, having said all this, Peter, James and John– the BIG THREE during Jesus’ ministry... pillars (a phrase implying ‘great teachers’) of the church gave him the right hand of fellowship, welcoming him into their leadership circle. Right hand meant a solemn vow had been made in trust. Fellowship meant a “partnership.”
Here in our churches we offer the “right hand of fellowship” too. Though it isn’t biblically required for membership, when someone becomes a member, we want to show them that we are now partnering together– and that we trust one another and are working together to advance the Kingdom of God as a team.