ISB ~ 1 Corinthians 9 v20

I became as a Jew:Paul continued to maintain certain Jewish traditions after becoming a Christian (Acts 16:3; 21:1726). Strictly speaking, this was unnecessary; yet Paul wanted to convert his kinsmen by removing whatever might turn them away from the gospel (1 Cor 10:32). Ethnically, Paul was an Israelite of the tribe of Benjamin (Rom 11:1; Phil 3:5).