“For we are the circumcision, who worship by the Spirit of God and glory in Christ Jesus and put no confidence in the flesh …” (v3). Paul assured the Philippians that no matter their ethnic background, they were “the circumcision” – shorthand for Israel, the people of God – because of their faith in Jesus Christ. They should avoid those who taught that Old Testament rituals were necessary (v2). Paul had done all of that as a “Hebrew of Hebrews” (v5) and counted it garbage in comparison to knowing Jesus Christ (v7-9).
No ethnic identity or religious ritual can make us favored by God. Instead, by putting our faith in Jesus, we receive His righteousness and become part of God’s family (v9).