Scripture
And you know that we treated each of you as a father treats his own children.
Observation
Paul reminds the Thessalonians of his conduct amongst them. He worked hard to support himself so he wouldn't be a burden to them. He worked with integrity, making sure that his conduct was above reproach.
Paul's attitude was like a father to the believers in that place. He loved them and encouraged them to live God's way. Therefore, Paul is thankful to God that they believed his words as being from God, and that His word is continuing to work amongst them.
Application
All those who claim to speak or work for God should take note of Paul's attitude and follow his example.
Paul never expected financial support from anyone. He tried to pay his own way, supporting himself by working at his trade. This is not to say that it is wrong for people to be in full time ministry. Sometimes however it is possible for a sense of entitlement to creep into our attitudes. Some ministers and missionaries expect to be rewarded in particular ways, or given certain recognition. Like Paul we need to walk in humility and not expect anything out of the ordinary in terms of financial support from the people we minister with.
Paul carried the spirit of a father, which is the true apostolic grace. Anyone who calls themselves an apostle who does not consider themselves to be a father to their people is not worthy of the calling. A father gives himself to a child. A father teaches, equips and mentors a child, releasing them into maturity. That is the true role of leadership in the christian community.
Prayer
Lord, as a leader grant me the heart of a father to those whom you have given me responsibility for. May I be a blessing not a burden, a source of joy not a cause for resentment. Amen.