Your Father Loves You by James Packer, (Harold Shaw Publishers, 1986), page for March 2.
What is meant by fellowship in this verse? Gossip? Cups of tea? Tours? No. What is being referred to is something of a quite different order and on a quite different level. "They met constantly to hear the apostles teach, and to share the common life, and break bread and to pray. A sense of awe was everywhere. All whose faith had drawn them together held everything in common. With one mind they kept up their daily attendance at the temple, and, breaking bread in private houses, shared their meals with unaffected joy as they praised God" (Acts 2:42-47>, New English Bible). That is fellowship as the new Testament understands it, and there is clearly a world of difference between that and mere social activities.
The Greek word for fellowship comes from a root meaning common or shared. So fellowship means common participation in something either by giving what you have to the other person or receiving what he or she has. Give and take is the essence of fellowship, and give and take must be the way of fellowship in the common life of the body of Christ.
Christian fellowship is two-dimensional, and it has to be vertical before it can be horizontal. We must know the reality of fellowship with the Father and with his Son Jesus Christ before we can know the reality of fellowship with each other in our common relationship to God (1 John 1:3>). The person who is not in fellowship with the Father and the Son is no Christian at all, and so cannot share with Christians the realities of their fellowship.