The concept of fellowship is widely misunderstood, being thought to be little more than christian social activities. In fact it stems from our living relationship with God. 1 John 1:1-3 reads (NASB) "What was from the beginning, what we have heard, what we have seen with our eyes, what we beheld and our hands handled, concerning the Word of life - and the life was manifested, and we have seen and bear witness and proclaim to you the eternal life, which was with the Father and was manifested to us - what we have seen and heard we proclaim to you also, that you may have fellowship with us; and indeed our fellowship is with the Father, and with His Son Jesus Christ,...".
The word "fellowship" in English is not a word with a clear meaning for most people, because it is not in everyday secular use. Such usage as it has seems derived from its religious use. The situation was very different for the Greek word, kiononia", at the time that the New Testament was written, and was the word used for, amongst other things, for a business partnership. The origin of the word shows it means "to have things in common", and if we apply this meaning to the 1 John 1 passage just quoted, it becomes alive. What John is telling us is that the basis of christians' relationships with each other and with God is that they have some very important things "in common".
Amos 3:3 says "Do two men walk together unless they have made an agreement" (NASB, margin) or "unless they be agreed" (RSV). We can only walk the same way as somebody else for any length of time if we are travelling in the same direction, and have much the same goals. If we do not then we will soon part, at least as far as those activities are concerned.
When we think generally about the people we know, that we like to be with, to do things with, we find that it is because we have something in common with them. Thus we find people who share the same interests are drawn to each other and do things together. Indeed it is hardly possible to have a relationship at all without some commonality of this sort. Most people have relationships with different people for different reasons: each of our friends relate to us for different things, and there may not be any real overlap between my relationship with one person and my relationship with another. For instance, there is usually very little overlap between my friends from the car club and those at church. This can lead to very difficult situations if I have to relate to both types of friends at the same time, and try to help them to find something which they can say to each other - the only thing which they have in common is their (very different) knowledge of me! We generally show to others only those parts of us which we know the other person is comfortable with, those things which we have in common.
So what is it that the christian has in common with his fellow believer? He is a member of the same family, having been born of God and having therefore received "eternal life" (1 John 1:2). This is why the basis of the relationship between christians depends on the reality of their relationship with the Father and the Son (1 John 1:3). Without the reality of this family relationship, there is no christian fellowship, though there may be a relationship between people on some other basis - such as a natural liking for theology, religious observances, or a common set of moral attitudes.
Natural family relationships are not always easy, since we would not necessarily chose those people to be our special friends. We do, however recognise that the basis of our family relationships is our common origin. The same is true of spiritual relationships, sometimes we are able to recognise that another has the same Holy Spirit which we received, even though we may find their outlooks are, to our mind at least, distorted. We can recognise their reality, but with such as these we may find it hard to work effectively. On the other hand we sometimes find that we superficially have quite a lot theologically in common with someone, but are aware that the spirit they have is not the same as ours. We should be wary of such people: we should be foolish to work with these.
1 Cor 12 makes clear that different parts of the body of Christ have different functions. Extending Paul's analogy, we note that the relationship between the foot and the ankle is much closer than that between the hand and the foot. Nevertheless through the rest of the body these diverse parts are ultimately connected, though they may only rarely have direct contact. This helps us to see that we should not even attempt to relate to all other christians at the same level of intensity - even Jesus had three special disciples - Peter, James and John, among the twelve. We have different jobs to do, and we need to see with whom we should be most closely connected. As in the body these connections are not for the pleasure of the individual parts but for a working together for the benefit of the whole, with each individual part, separately "holding fast to the Head", Christ. This corresponds in the human body to the control which the head exercises over each part of the body through the nervous system. This passage emphasises the commonality of a working relationship - bringing us back to the business partnership idea conveyed by the Greek word for fellowship.
Of course, the people we shall be working together most closely with will generally be those with whom we have most in common. The more we have in common the more we are able to share with them, and the more effectively we understand how we fit together in the work. If each christian concentrated on developing effective working relationships with these few people to whom we are drawn, we should soon find the church being far more effective. While we are trying to fit in and accommodate all sorts of people to find a vision common to all, we will find we can only do those few, probably very few, things which all have in common. This is not the way to accomplish anything. Effective working needs specialising groups - as shown by the small but highly effective apostolic teams of New Testament times.
Each christian therefore should consider: