In my book, Your Church Is Too Small, I make a link between unity and mission based upon John 13:34-35; 17:20-23 and 20:21. It is clear that the unity Jesus prayed for in John 17 was intended to lead the world to understand that the Father had sent the Son (17:21). My discovery of this principle was rather simple but totally life-transforming. One does not need a theological education to see it in the text. Our relationships with Christians are meant to model the Father and Son relationship in the incarnation in such a way that the world will see the reality of God’s love.
The New Commandment, given in John 13:34-35, underscores the same point in the clearest words possible. When we love one another Jesus says that “everyone will know that you are my disciples” (13:35). Francis Schaeffer was right when he said this “love” was “the mark” of the Christian. Yet far too few of us really believe this and even fewer of us make it our actual practice. No matter what the situation is you can never go wrong if you love as Jesus taught you to love. This is not in doubt. Many doctrines are not so clear but this is as clear as can be. Maybe it is the clear portions of Jesus’ teaching that really trouble us since we love to major on the one’s that create disagreements.
This truth is so central that it acts as a governing principle in all our actions. I decline to participate in many of the inter-evangelical and Protestant/Catholic quarrels because of this love. I hold opinions, sometimes strong ones. I believe in revealed truth and will not sacrifice it. But all of this firm belief still falls under the New Commandment to love one another. Why is this so hard for us to grasp? Why do we have so many excuses for not loving others in the church? I think the answer is self-evident.