Most often when we hear the word harmony we think of the musical term which is defined as, “The combination of simultaneously sounded musical notes to produce chords and chord progressions having a pleasing effect." When there is harmony it sounds good.
The opposite of harmony is dissonance. Dissonance can be defined as a, “...tension or clash resulting from the combination of two disharmonious or unsuitable elements.” When there is dissonance the sound is not good.
When there is harmony in the church it is good and great things can be accomplished because we are on the same page, but when there is dissonance the church is greatly hindered. One of the primary ways the devil attacks the church is attempting to disrupt the harmony that is there. In Luke 11:17 Jesus said, "Any kingdom divided against itself is laid waste; and a house divided against itself falls."
In Acts 2 we see a model of how the church lived in harmony with one another.
And all those who had believed were together and had all things in common; and they began selling their property and possessions and were sharing them with all, as anyone might have need. Day by day continuing with one mind in the temple, and breaking bread from house to house, they were taking their meals together with gladness and sincerity of heart, praising God and having favor with all the people. And the Lord was adding to their number day by day those who were being saved.
I am sure they had disagreements and disputes, but they were still of one mind. This does not mean they were not individuals who at times had their own opinions and ways of doing things. It means they understood the kingdom was bigger and greater than any single individual.
If the church of today can learn to be of one mind, learn to live in harmony, it will make an impact upon the world we cannot begin to imagine.