Paul opens the chapter: Finally, my brothers, rejoice in the Lord! He then gives a strong warning against false teachers who said that outward signs, like circumcision (an outward sign in the law of Moses), made people right with God. Paul says that true believers worship God in the Spirit, rejoice in Christ Jesus, and have no confidence in the flesh. Paul himself had every outward reason for confidence: circumcised the eighth day, of the tribe of Benjamin, a Hebrew of Hebrews, a Pharisee, and blameless in the righteousness of the law. He had even persecuted the assembly.
Then comes a great turn. Paul says that whatever was gain to him he now counts as loss for Christ. He counts everything as loss for the excellency of the knowledge of Christ Jesus, his Lord. He wants to be found in Christ, not having a righteousness of his own from the law, but the righteousness which is from God by faith. His deepest desire is to know Christ and the power of his resurrection.
Paul is honest: he has not already obtained or been made perfect. But he says, one thing I do: forgetting the things which are behind and stretching forward to the things which are before, I press on toward the goal. He urges the believers to follow his example. He grieves over many who live as enemies of the cross. But believers have a different hope, for our citizenship is in heaven, from where we also wait for a Savior, the Lord Jesus Christ.