Philippians 4:15
Now ye Philippians know also, that in the beginning of the gospel, when I departed from Macedonia, no church communicated with me as concerning giving and receiving, but ye only. Now ye Philippians know also, that in the beginning of the gospel, when I departed from Macedonia, no church communicated with me as concerning giving and receiving, but ye only.
In the beginning of the gospel means at the start of Paul's gospel work, when he first departed from Macedonia soon after the Philippians' conversion. Giving and receiving means financial partnership with him, sending support to meet his needs in gospel work. No other church did this; the Philippian church alone shared with him in this way.
Their aid expressed generosity and sympathy and helped Paul and the apostles in affliction, want, hardship, and financial need. Their partnership was repeated and continued after he left, sending him aid when he was in need at Thessalonica. They repeatedly sent gifts that reached him at Corinth and later while he was a prisoner in Rome, and their own poverty did not stop them from giving, even when he refused support elsewhere to avoid giving his enemies grounds to accuse him of seeking personal gain.