For ye have heard of my conversation (conduct) in time past in the Jews’ religion, how that beyond measure I persecuted the church of God, and wasted it. And profited in the Jews’ religion above many my equals in mine own nation, being more exceedingly zealous of the traditions of my fathers. ~ Galatians 1:13-14

Paul makes the above statement after telling the Galatians that he marveled that they were so soon being removed from Him who had called them to the grace of Christ, unto another gospel.

I marvel that ye are so soon removed from him that called you into the grace of Christ unto another gospel: Which is not another; but there be some that trouble you, and would pervert the gospel of Christ. But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed. As we said before, so say I now again, if any man preach any other gospel unto you than that ye have received, let him be accursed. For do I now persuade men, or God? or do I seek to please men? for if I yet pleased men, I should not be the servant of Christ. But I certify you, brethren, that the gospel which was preached of me is not after man. For I neither received it of man, neither was I taught it, but by the revelation of Jesus Christ. ~ Galatians 1:6-12

Paul is telling the Galatians at the very outset of his letter that those in the Jews religion, in which he once excelled above his peers, are preaching another gospel. In Galatians, Paul is dealing with the false teachings of those who were advocating Jewish identity (via circumcision and adherence to the law) rather than glorying in Christ.

These religious Jews (aka, Judaizers) did not simply want to bring the Gentiles under some sort of “works righteousness” but rather, they were seeking to make Jewish proselytes of the Gentiles, and this was something that Paul rigorously opposed.

It wasn’t enough to these religious Jews that the Gentiles had believed the gospel and received the Spirit. The wanted the Gentiles to go beyond the cross of Christ and become Jewish proselytes (through circumcision and adherence to the Law).

It is this “Jewish supremacy” based on the Jew’s religion that Paul is countering so strongly in Galatians.  Jewish supremacy, such as Paul is addressing in Galatians, is in opposition to the truth of the gospel.

Because of the cross, there is no privilege of one ethnic group above another in the sight of God. In Galatians 5:11 Paul says, “And I, brethren, if I yet preach circumcision (the mark of Jewish identity) why do I yet suffer persecution? Then is the offense of the cross ceased.“

The issue of circumcision in the first century church wasn’t merely about “legalistic works” as we in the church today would refer to legalism. It was much more than that. It literally meant being converted, and becoming a Jew. It was for this purpose that the apostle Paul was being persecuted by those who preached circumcision. Paul preached that the cross alone could save and being circumcised or not being circumcised no longer had relevance with regards to being in covenant with God.

To put it another way, being a Jew or not being a Jew no longer had any bearing on who was God’s people and who wasn’t. God had abolished the separating wall between Jews and Gentiles in the death and resurrection of Jesus. God’s people are no longer of one ethnic group in the flesh, but rather are people of every nationality united in one new man, in one body of believers, in Christ Jesus. What matters now is being a new creature in Christ Jesus.

https://michaelbattle65.wordpress.com/2016/02/26/one-new-man-in-christ/