Unity should be a distinguishing mark of Christians. It's in the Bible, Philippians 2:1-2, NIV. "If you have any encouragement from being united with Christ, if any comfort from His love, if any fellowship with the Spirit, if any tenderness and compassion, then make my joy complete by being like-minded, having the same love, being one in spirit and purpose."
Jesus prayed that His people would be unified. It's in the Bible, John 17:11, NIV. "I will remain in the world no longer, but they are still in the world, and I am coming to You Holy Father, protect them by the power of Your namethe name You gave Meso that they may be one as We are one."