One of the things that stands out in Paul's letter to the Philippians is their deep affection for one another that stems from their partnership in the gospel.
'I thank my God every time I remember you. In all my prayers for all of you, I always pray with joy because of your partnership in the gospel from the first day until now, being confident of this, that he who began a good work in you will carry it on to completion until the day of Christ Jesus. […]