Summary: We must be very clear on the fact that Jesus was very passionate about the unity of the church that He had to take it to God in prayer.
Sometimes ago, I did a write up on the subject "Crisis in Christ". It borders on the competition and irreconcilable difference among the supposed believers in Christ and the different denominations they belong to. There appears not to be an end to the war tearing the body of Christ apart. Today, the believer's first point of commitment is his/her denomination rather than Jesus and unfortunately, that is what today's anointed men of God preach. We have all forgot that Christians are so called because they surrender to the Lordship of Jesus and not because they belong to one denomination or the other. Of course, it is the last days and Christians are falling away from the love of Christ and becoming lovers of selves and denominations rather than lover of Christ (1Tim3:1-2).
The seventeenth chapter of the book of John contains the prayer of Jesus for all Christians and everything in that prayer centres on the unity of the church. "Holy Father, keep through thine own name those whom thou hast given me, that they may be one, as we are. John 17:11b" Every other prayer was said to buttress that fundamental prayer of unity of the church.
By the way, we must be very clear on the fact that Jesus was very passionate about the unity of the church that He had to take it to God in prayer. It therefore implies that anyone, irrespective of the position occupied or anointing carried, that is working directly or indirectly against the unity of the church is the enemy of Jesus and of the cross. Church politicians, beware! If God did not spare His Son to bring redemption to mankind, He will not spare anyone or group who might want to hinder the fulfilment of that redemptive work.
There are two components of the prayer that I think we, as individual Christians, and every church leader have to take to heart. They are what I call "The Why and How of Church Unity".
Apart from other reasons given in that passage for the prayer of unity for the church, the plea for the church to make it to Heaven stood clearly out (verse 24). It means that it is in unity that the body of Christ can attain this feat. Jesus Christ had assured the church that He was going to prepare a place for us in His Father's house and that He would return to take us there to dwell with Him (John 14:1-3). We will therefore see from this prayer that lack of unity in the church can stand in the way of that promise. The reason He prayed the Father to help the church remain as one. Jesus even affirmed in Matthew 12:25-26 that any kingdom or house divided against itself cannot stand. If the purpose of Him presenting the saints before His Father must therefore be achieved, the saints must be united.
The other component of the prayer that stands for the "How" is expressed in the last verse and it is love. The only thing that can ensure the kind of unity that will not abuse the purpose of Jesus' redemptive work is the God kind of love. Love overcomes the strongest barriers and pardons the most terrible of sins. Love does not breed fear nor discord. It does not matter the gifts or callings that we profess to have, love surpasses them all. And without love, the purpose of all other gifts and callings will be as good as defeated (1Cor 13; Eph 4:11-16). It is in the love of God that the church being knitted together can be preserved from the evil of this world. If we, individually and collectively, have and exhibit the love of God one to another, evil will not be permitted amongst us, the body of Christ will grow faster because the spread of the gospel will become astronomical, the joy of the Lord will be fulfilled in the church and unity of the body of Christ will be inevitable.