Greetings,
One of the strongest comments Jesus made on missions is found in John 17:20-23, "Neither pray I for these alone, but for them also which shall believe on me through their word; That they all may be one; as thou, Father, art in me, and I in thee, that they also may be one in us: that the world may believe that thou hast sent me. And the glory which thou gavest me I have given them; that they may be one, even as we are one: I in them, and thou in me, that they may be made perfect in one; and that the world may know that thou hast sent me, and hast loved them, as thou hast loved me."
In this passage, Jesus hinged the credibility of the missionary message on our oneness in Him. Four times, He prayed that God would enable us to demonstrate a marvelous unity that will make Christ Himself visible to the world.