What a statement! It can be seen as arrogant or it can be understood as someone with a death wish—a willing target for the opposition. Nevertheless, if the Bible is the word of God, I (we who believe in Jesus) am not only the evidence that God sent his Son into the world (John 17:21), but the evidence that God loves those who are his (John 17:23), and the evidence that, in sending his Son, God loves the world (John 3:16). Jesus left no artifacts that archaeologists could dig up, no personal testimony written by his own hand that would tell the world what God wants us to know. Rather, he has left me, and I am one of many brethren. We are the living testimony of what God is all about. Imagine!
Jesus’ great commandment in John 13:34 tells us that our love for one another is the only evidence God gives to the world that we belong to Jesus, and, if we do love one another, the world will accept our unity as that evidence. In other words, my relationship with Jesus (God) is evidenced only in how I love my brethren, and only thereby can I be known as his disciple.
Often we are able to see the traits of a father in the son he sired. It may be how a person looks or how he acts, but evidence of his father is found in him. A king is addressed as sire. I have wondered why that is so, but as I think upon that in the context of Jesus’ statement in John 13:34, it can mean only that the loyalty of the king’s subjects to their lord is evidence they are his; i.e. their patriotism is the evidence they are one and stand behind him. He is their sire! The question is: is there enough evidence in me—in my life, in what I say and do—to tell the world I am a disciple of Jesus? Is there enough evidence in my behavior toward my brethren that would tell others I belong to Jesus and stand behind him? In John 14:9 Jesus claimed that anyone who has seen him has seen the Father. Can I say the same about my own life—that anyone who has seen me has seen Jesus? What a humbling thought!
Four times Jesus prayed that we would be one as he prayed to the Father in John 17. First, in John 17:11 Jesus prayed that God would keep those he has given Jesus—i.e. that he would guard or protect them in order that they (we who believe) would be one in the same manner as Jesus and the Father are one. What does that mean? I think it refers to the image of God in Adam and Eve. Eve was brought out of the man and presented to him and was found to be like him (Genesis 2:21-23). Jesus was brought (or sent) out from God and presented to the world (John 16:27) and was found to be like God (John 14:9). Jesus is praying that we would remain in him (John 15:4-5), bearing fruit that would show we are his.
Secondly, Jesus prayed we would be one, as the Father and Jesus are one—he being in the Father and the Father in Jesus—that our unity in Christ who is in the Father would be evidenced in the world’s recognition that Jesus was sent by God (John 17:21). How can the world know that God sent Jesus—and only Jesus? The world will know only if we who believe in Jesus remain united in him.
A third time Jesus prayed that we would be one in John 17:22, saying that the glory the Father had given Jesus, Jesus had given to those who believe in him, but what does this mean? What glory had the Father given Jesus that Jesus was able to pass on to us? I think it had to do with Jesus seeking the Father’s glory rather than his own (John 7:18; 8:50). In seeking to glorify the Father, Jesus was glorified himself (John 11:4). Herein is our glory found: when all we do is to reveal the glory of Jesus to the world. Jesus prayed that God would return to him the glory he once had with him before the world existed (John 17:5), and then he prayed that the Father would permit those he had given to Jesus to be with him where he is (i.e. in the Father) that they (we who believe) would be able to witness Jesus’ glory and tell it to the world (John 17:24)
Finally, Jesus prayed we would be one in order to become perfect (John 17:23)—i.e. fully mature in him. In other words, by remaining in Christ, we would grow up in his love; we would become fully mature in the love of God, and in so doing be individually and collectively a perfect image, i.e. a grown up or mature image, of what God is like in one or several facets of his character, so the world could know him in one of us or see him in the whole body of believers.
 As I said HERE, this current theme about the person of Jesus is based upon the book: The Jesus Style by Gayle Erwin. They are my thoughts about his book. He may or may not agree with the impression his book has made upon me, but I thoroughly enjoyed reading what Gayle wrote and recommend his book to anyone who is looking for a good read about Jesus.