Summary: We are called to unity, not just to be together. No one was ever called to walk this Christian life alone. Every member of the body is responsible to maintain the unity. We maintain unity by individually and collectively keeping our focus on Jesus.
Concerning unity in the church, one of my favorit commentators and Christian authors, A.W. Tozer, the great evangelist and Christian theologian from 60 years ago, commented: Has it ever occurred to you that one hundred pianos all tuned to the same tuning fork are automatically tuned to each other? They are of one accord by being tuned, not to each other, but to another standard to which one must individually bow. So one hundred worshipers meeting together, each one looking away to Christ, are in heart nearer to each other than they could possibly be were they to become “unity” conscious and turn their eyes away from God to strive for closer fellowship.
Think about it, If we are all individually looking to Jesus for all our thoughts, words and actions, we would have peace and harmony with one another. But what happens when one or more takes their eyes off Jesus? Petty squabbles happen, then it becomes us versus them.
Paul was dealing with a church full of Jews and Gentiles – two groups that in that time and culture, never mixed. Our passage today deals with unity in the Body of Christ.
Ephesians 4:1–6 (NKJV) I, therefore, the prisoner of the Lord, beseech you to walk worthy of the calling with which you were called, 2 with all lowliness and gentleness, with longsuffering, bearing with one another in love, 3 endeavoring to keep the unity of the Spirit in the bond of peace. 4 There is one body and one Spirit, just as you were called in one hope of your calling; 5 one Lord, one faith, one baptism; 6 one God and Father of all, who is above all, and through all, and in you all.
A visitor to a mental hospital was astonished to note that there were only three guards watching over a hundred dangerous inmates. He asked his guide, “Don’t you fear that these people will overpower the guards and escape?” “No,” was the reply. “Lunatics never unite.”
Unfortunately there are many churches that resemble mental ward, everyone doing their own thing, to the exclusion of everyone else. Remember how we talked about how the church, the local body of Christ is Jesus physical presence in this world? We at Rosemont, are not merely part of the body Christ, but we are the very physical manifestation of Christ in this community. How did Jesus say that the world will know that we are His disciples?
John 13:35 (NKJV) By this all will know that you are My disciples, if you have love for one another.”
This is not the first time I have used this verse and it won’t be the last. We must continually remind ourselves of this fact. As the local body of Christ, we have a great responsibility to our church and to the community around us. Dis-unity will destroy that witness and mar the very imagine of Jesus we share.
But unity is not a simple matter of simply loving one another. Many people today attempt to unite Christians in a way that is not biblical. For example, they will say: “We are not interested in doctrines, but in love. Now, let’s forget our doctrines and just love one another!” But Paul did not discuss spiritual unity in the first three chapters; he waited until he had laid the doctrinal foundation. 
Chapter 4 of Ephesians is the turning point in this epistle. The first three chapters, Paul laid down the foundation, the doctrine of salvation, how we relate to God and to each other. Now Paul turns to the practical: how this works out in everyday life. Remember Paul is dealing with Jews and Gentile who did not culturally mix.
Ephesians 4:1 (NKJV) I, therefore, the prisoner of the Lord, beseech you to walk worthy of the calling with which you were called,
Numerous places in the letters of Paul, in his prison epistles, he refers to himself as a “prisoner of the Lord.” In chapter 3:1 he said he was a “prisoner of Christ Jesus for you Gentiles.” Paul was in prison in Rome because of his desire to serve Christ, regardless of the cost. Paul gave up his freedom to follow Jesus, and he expected others to do the same.
“I, therefore” - using himself as the example in light of all the doctrine he covered in the first 3 chapters, “beseech you to walk worthy of the calling with which you were called” We were called by the Creator of the universe, His righteousness placed on us, so that we can stand confidently before God, that was the call. We are to walk worthy of that call. For Paul, to do otherwise was unthinkable. Many think they filled the square of walking the aisle, shaking the preacher's hand, saying a prayer, and being dunked in the baptismal pool, then back to life as before: