Lifting up his eyes to heaven, Jesus prayed saying: “I pray not only for these, but also for those who will believe in me through their word, so that they may all be one, as you, Father, are in me and I in you, that they also may be in us, that the world may believe that you sent me. And I have given them the glory you gave me, so that they may be one, as we are one, I in them and you in me, that they may be brought to perfection as one, that the world may know that you sent me, and that you loved them even as you loved me. Father, they are your gift to me. I wish that where I am they also may be with me, that they may see my glory that you gave me, because you loved me before the foundation of the world. Righteous Father, the world also does not know you, but I know you, and they know that you sent me. I made known to them your name and I will make it known, that the love with which you loved me may be in them and I in them.”
With this prayer for unity, Jesus concludes His prayer; and then begins a discourse on the same subject: "A new commandment I give to you, that you love one another."
This does not express perfect likeness to God, but only likeness as far as it was humanly possible; as when He says, "Be you merciful, even as your Father, which is in heaven, is merciful." And how is this command carried out? That all who believe through the Apostles are one.
For there is no scandal so great as division, whereas unity amongst believers is a great argument for believing; as Jesus had said, "By this shall all men know that you are My disciples, if you have love one to another." For if they quarrel, they will not be looked on as the disciples of a the God of peace. And I, He says, not being a peacemaker, they will not acknowledge Me as sent from God.