“We ourselves are Jews by birth and not Gentile sinners; yet we know that a person is not justified by works of the law but through faith in Jesus Christ” (v15-16). Some Jewish Christians were having trouble accepting Gentiles because they didn’t really see themselves as needing the same grace. They thought that God was pleased with their rule-keeping and that the uncircumcised Gentiles were second-class (v4). But Paul said that our pride before God is worthless.
“I have been crucified with Christ. It is no longer I who live, but Christ who lives in me” (v20). We can’t please God by being part of the right group; we must each put our whole trust in Jesus.