This is one of Paul’s reasons for giving thanks to God, which is that, from day one, the Philippians contributed to the spread of the gospel. They have become partners in the great work of proclaiming the message of and about Jesus Christ. Their partnership may have manifested itself in several ways: intercession, hospitality, suffering for the gospel, evangelism in their own environment. Also through their financial and material support. See his expression of thanks for the help he received in Philippians 4:14–18.
5 because of your partnership in the gospel from the first day until now.