For we are the circumcision, who worship by the Spirit of God and glory in Christ Jesus and put no confidence in the flesh— (Philippians 3:3, ESV)A little explaining is in order here:
When Paul traveled throughout the Roman Empire, he would quite often head into the Jewish communities first. Many times preaching and teaching at a Jewish Synagogue. And there would be Jewish converts to Christianity, but for them, it would many times be incorporated into their pre-existing beliefs.
Lest we be too quick to judge, consider first of all that Christ was truly a fulfillment of the Law and the Prophets. Christ was, in reality, the messiah that they had all been waiting for. So, it would only make sense, at first glance, that nothing of their religious practices should change. I mean, why would it? Should we not continue to obey the Ten Commandments? Were there not important aspects of the Law that should continue to be obeyed?
Consider, as well, there were always Jewish Proselytes: There were always those who had heard the truths of the Word of God and had believed them. And all of these converts to the Jewish belief system would become, in a sense, Jews. Circumcision was sort of the key word that encompassed all of the changes that needed to be made to become a Jew. (Can you blame them for emphasizing this?!?)
But now Paul is teaching that circumcision doesn't need to be done. He is teaching, in fact, that the true people of the circumcision, were not necessarily those who had been circumcised in the flesh, but those who were now worshiping the true and living God, by the Spirit of God, in the person of Jesus Christ.
The important aspect of this passage is that Paul is teaching us not to put confidence in the flesh. The real issue was that many were putting all of their assurance of their faith in what HAD been done. We still struggle with this today. There are many who are convinced of their own salvation because of what they have done. They have prayed a prayer. They have gone to church. They have been baptized. Sometimes it is really thin... whether it is because their parents went to a certain church or simply because they aren't from another religion... Their confidence is still in the flesh because their confidence is because they have done all of the steps that they think needs to be done.
On the flip side to this is one who has put all of their confidence, not in what they have done, but in what Christ has done. This confidence takes the form of ongoing worship of Jesus Christ.
Where is your confidence? Are you convinced of your own salvation because of a checklist of items that you have come to believe are the necessities of salvation?