Paul warns Christians against those who say circumcision is necessary for salvation. He emphasizes that true circumcision and worship of God comes through faith in Christ by the power of the Holy Spirit, not human effort to please God through works. Paul contrasts his own past religious credentials and efforts to obey the law with faultless perfection against knowing Christ and relying on what He has done. Living by faith means trusting in God's acceptance of us, rather than trying to earn His favor through good works or spiritual disciplines. Those who focus on pleasing God through their own efforts are not worshiping in spirit and truth, but are exalting themselves, just as the Pharisee did.