"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. For even in Thessalonica ye sent once and again unto my necessity."
Paul is referring to the events of his second missionary journey described in Acts 17:1-9. At the point to which Paul is referring, churches had been established in the regions of Syria and Cilcia; however, for reasons not given, the only church to consider Paul's financial need was that of Philippi. Also, the church's charity was not a singular event. Numerous times they sent relief to Paul by the hands of messengers.
The Philippian church could have resented the fact that other churches were not sharing in the responsibility. They could have been angered by older churches in the faith that were not meeting an obvious need; but instead, the Philippians saw the need and met it. Neither bitterness nor self-pity kept them from doing right regardless of the failure of others. When others are not stepping up to meet an obvious need, it may be easy to think "why should I take on all this burden?" Seeing fellow believers fail during a time when they should be taking on responsibility can make a man angry; however, God never cursed a man for having a heart of charity. He never rebuked an individual for stepping in when He has provided the grace to do so. People fail. Sometimes the reasons are obvious and sometimes they are not; but one thing is for certain, God knows the reasons for everything, and He is able to sort out and to judge the works of all men (Ecclesiastes 12:14). The believer need only keep his eyes on the Lord and obey the call to service as God gives grace and opportunity.