Testify

There are many times in the Bible that we see testimony about Jesus both from believing and unbelieving individuals, but perhaps the most important is the testimony Jesus gives about himself.

After being hassled for working on the Sabbath Jesus says:
“If I testify about myself, my testimony is not true. 32 There is another who testifies in my favor, and I know that his testimony about me is true. (John 5:31:32 NIV)
Jesus notes that his testimony wouldn't be valid if he was the only one to talk about himself. That doesn't mean that Jesus isn't telling the truth, just that if we were talking in a courtroom situation, and it was just Jesus' testimony there wouldn't be sufficient evidence.

And so he points to John:
“You have sent to John and he has testified to the truth. 34 Not that I accept human testimony; but I mention it that you may be saved. 35 John was a lamp that burned and gave light, and you chose for a time to enjoy his light. (John 5:33-35 NIV)
John constantly said that one was coming that would bring light to the world, and that it would be bigger than him. Then when Jesus came he proclaimed boldly that Jesus was the person he was talking about. There was no way anyone could possibly miss that Jesus was the guy he was talking about, yet they did. And it's not like they just didn't like John the Baptist, Jesus points out that they did enjoy John the Baptist, and so should have clearly understood that Jesus was the one that JTB was talking about, yet they didn't, they chose not to.

But he doesn't stop there, he continues, ramping up the quality of the testimony, like a good lawyer:
“I have testimony weightier than that of John. For the works that the Father has given me to finish—the very works that I am doing—testify that the Father has sent me. (John 5:36 NIV)
Jesus points out that what they just witnessed proves that he is who he says he is. This whole discussion started because Jesus healed a crippled man on the Sabbath, that healing alone should be enough to prove that Jesus is who he says he is. Who else but God could heal, and yet Jesus does it.

Jesus continues pointing to ever stronger testimony:
And the Father who sent me has himself testified concerning me. You have never heard his voice nor seen his form, 38 nor does his word dwell in you, for you do not believe the one he sent. 39 You study the Scriptures diligently because you think that in them you have eternal life. These are the very Scriptures that testify about me, 40 yet you refuse to come to me to have life. (John 5:37-40 NIV)
Jesus points to the Bible, he knows his audience, he knows that they will be always looking at the scriptures and so he reminds them that those are God speaking to them, which they would recognize, then he points out that they have been speaking about him this whole time. Why then do they choose not to come to him?

Jesus' testimony about himself is valid, he is who he says he is and we can just look at his actions to back that up. But beyond that there is an entire cannon of prophets who have spoken about him, not to mention the testimony from many of his contemporaries (both hostile and non-hostile) we can trust his testimony.