Two other things mentioned in verse 6 do not avail.
According to verse 6 there are two kinds of people “in Jesus Christ.” There are two kinds of Christians, two kinds of believers or two kinds of church members: the circumcision, believing Christians of a Jewish background; and the uncircumcision, believing Christians of a Gentile or pagan background.
In the New Testament “circumcision” is almost synonymous with “Jew.” Circumcision was the Jewish ceremony of initiation or the Old Testament sign of the covenant. In Paul’s day it was still the sign that distinguished the Jews from the other nations and the Jews boasted in their circumcision. The Judaizers thought that circumcision was so important that the Gentiles must be circumcised in order to be saved and justified before God (Acts 15:1). Moreover, circumcision signifies and represents the whole law, which is clear from the context: “Behold, I Paul say unto you, that if ye be circumcised, Christ shall profit you nothing; for I testify again to every man that is circumcised, that he is a debtor to do the whole law. Christ is become of no effect unto you, whosoever of you are justified by the law; ye are fallen from grace” (Gal. 5:2–4).