Phil 1:5

1:5 your partnership. The Philippians’ financial support is especially in view (4:10–20).

in the gospel. The word “gospel,” Paul’s favorite term for his message, occurs nine times in Philippians (more, proportionately, than in any other letter). Paul and the Philippians are bound together by their common commitment to the gospel (v. 7).

from the first day. That is, since the gospel first came to Philippi (4:15; Acts 16:12–40).