The central theme of the Bible is Jesus. The greatest and most humble of Christians have recognized this profound truth. Jesus came to call people to be his disciples from every tribe, nation and tongue (Revelation 14:6). He is the Shepherd and we are his sheep. He calls his sheep by his Spirit, through the good news of the gospel, into the communion of the church. P. T. Forsyth, a famous theologian more than a century ago, rightly said, “The unity of the church lies not in itself but in its message, in the unity of the gospel that made the church.”
The gospel that specifically called the church into existence is the gospel of the kingdom (cf. Matthew 4:23; 5:3; 6:10; Mark 1:14−15; 4:11. 26, 30; 9:47; Luke 4:42−43; 6:20; John 3:3, 5). This kingdom is God’s reign. What is promised to the church in the New Testament is not the kingdom but the Holy Spirit whose presence gives witness to the reign of God. The Spirit leads the church into the fullness of truth by keeping the church alive within the love and power of Jesus.
When the church recovers the centrality of the gospel of the kingdom it will cease to think of itself as the end of Christ’s mission but as the means to a much greater missional end. In the New Testament a local church did not exist as an end in itself. Each congregation existed for the whole church and the church existed to serve the kingdom of Jesus in a town, city and region. Jesus commanded his disciples to pray, “Your kingdom come” and told them to “seek first the kingdom of God.” He expected his kingdom to have a profound influence in the world. Through fear and misinformation I believe we miss this kingdom message. We limit its expression to our institutional church thereby treating other churches and Christian leaders as our competition. And even when we have stressed the gospel of the kingdom we have stressed the individual and personal aspects of it rather than the corporate and communal. Furthermore, we have concentrated on the moral and spiritual aspects to the virtual exclusion of the material and physical. This had led most Western Christians to divide life into activities that are seen as secular and sacred. Our preoccupation with ourselves has kept us from seeing that the gospel is actually about Christ’s reign, not my personal satisfaction and success.
We must re-center our lives on the incarnate person of Jesus Christ who is the essential characteristic of true unity. This is why his prayer for our unity in John 17 is so closely linked with his mission in John 20:21: “As the Father has sent me, so I am sending you.”
How did the Father send Jesus? He came in weakness, in profound humiliation, and as man who was subjected to all temptation. He was, in short, completely vulnerable and deeply relational. He was even called “the friend of sinners” (Matthew 11:19). And in the most relational and intimate of all contexts he called his closet disciples his “friends” (John 15:14).
The incarnation of Christ is thus the essential characteristic of the relational identity that defines the oneness of the church Jesus prayed for in John 17. It is the real key to the unity factor. The indwelling presence of the Holy Spirit empowers this oneness, making it real in our experience. The gospel becomes the essential truth of our unity, that truth which holds us together in mission, since the disciples of Jesus are gospel people. As The Cape Town Commitment puts this:
The core of our identity is our passion for the biblical good news of the saving work of God through Jesus Christ. We are united by our experience of the grace of God in the gospel and by our motivation to make the gospel of grace known to the ends of the earth by every possible means (23).