and be found in him, not having a righteousness of my own that comes from the law, but that which comes through faith in Christ, the righteousness from God that depends on faith— (Philippians 3:9, ESV)This was truly how it always was. Righteousness had always come through faith. Paul evidences this in Romans when he discusses how Abraham... who, before the Law and before he was circumcised, had righteousness credited to him because he simply believed God. (Romans 4:3; Genesis 15:6)
Paul wants nothing more than to have this righteousness and to help other to see this. He wants to liberate them from the bondage of attempting to earn our own righteousness. He desires to teach and preach the good news of the gospel to the world.