In most of Paul’s letters he expresses his thankfulness to God for the believers to whom he is writing. As well he expresses thanks to God for His work and what He has done in various places. Paul’s gratitude spills over into joy especially in his epistle to the Philippians. Paul’s gratitude is for all things even when circumstances are not in his favor. Not only does he model thankfulness but he exhorts the believers to give thanks in and for all things. And so we should do likewise. 

Paul is confident that the work that God began in the Philippians will be completed. He bases this on both God and the response that the Philippians have had and continue to have in their partnership with Paul and God in the gospel. On the one had they are partnering with Paul; on the other hand, they are partnering with God in His mission. Their response gave Paul this confidence. Let us partner with each other and with God in his mission.