As is typical of Paul’s letters, he begins by expressing his thanks for the church in prayer. Most letters in the Greco-Roman world began with some sort of thanksgiving section in order to set the tone for the letter. Here Paul recalls his time with the church, probably going all the way back to his first visit to the city in Acts 16. He likely had other contacts with the church over the years.
The reason for his thanksgiving is the church’s partnership in the Gospel. A “partnership” (κοινωνία) is a close association of individuals, a fellowship. While contemporary English uses the word with the sense of a business friendship, or sometimes as a verb for a ministry asking for money (they want you to “partner” with them by giving money), the use of this word in the first century was more complex. It can be used, for example, to describe the marriage relationship (3 Macc 4:6) although this is not found in the New Testament. It is often used for close participation Phil 3:10, we “participate” in the suffering of Jesus; 1 Cor 10:16 the believer “participates” in the blood of Jesus; in 2 Corinthians 8:4 the readers are asked to “participate” in sending famine relief. The Philippian church has participated in Paul’s ministry by sending him financial support via Epaphroditus, a servant from their church.
Paul is confident God will bring their work to completion “at the day of Jesus Christ.” When the gospel was preached in Philippi God began to do something good, and Paul is absolutely confident that God will finish the good work he began. Having been persuaded, this is a perfect participle; Paul was persuaded that the members of the church. It is not the case that Paul was unconvinced until the church sent him some money!
Modern Christians might reading something like “good work” as a reference to ministry, maybe a mission goal, etc. But a “good work” in a Greco-Roman context would refer to doing some sort of civic project for the good of a community. Imagine someone donating a great deal of money and material to begin the building of a new public building for the good of the community, a museum or library. If the money ran out before the building was finished, this would be a shameful thing for the one who began the project.
There is a tower in Poland intended to be the new regional office of the Main Technical Organization in 1975. Work was stopped in 1981 due to civil unrest, but nothing has been done since to the 92 meter tall structure since. The building known as “Skelator” is too expensive to re-purpose or demolish. This unfinished project is an embarrassment to those who originally planned it.
In the case of the Philippian church, God began the project of building up the church and he will bring the project to a glorious completion on the Day of Jesus Christ. Paul is confident there will be no shame or embarrassment from a half-completed project in the case of this church since God himself is the builder and he cannot fail.
Paul therefore opens his letter with a look back at how the Philippian have already participated in his presentation of the Gospel but also forward to the completion of that partnership when those who are in Christ meet him in glory. Paul has this level of confidence because he knows the church also participates in God’s grace.