12 When Jesus spoke again to the people, he said, "I am the light of the world. Whoever follows me will never walk in darkness, but will have the light of life."
13 The Pharisees challenged him, "Here you are, appearing as your own witness; your testimony is not valid."
14 Jesus answered, "Even if I testify on my own behalf, my testimony is valid, for I know where I came from and where I am going. But you have no idea where I come from or where I am going. 15 You judge by human standards; I pass judgment on no one. 16 But if I do judge, my decisions are right, because I am not alone. I stand with the Father, who sent me. 17 In your own Law it is written that the testimony of two men is valid. 18 I am one who testifies for myself; my other witness is the Father, who sent me."
Jesus clearly makes right judgments, as they are based on the will of the Father, who is the perfect judge.
19 Then they asked him, "Where is your father?"
"You do not know me or my Father," Jesus replied. "If you knew me, you would know my Father also." 20 He spoke these words while teaching in the temple area near the place where the offerings were put. Yet no one seized him, because his time had not yet come.
Jesus continually makes it clear that it is not religion that will get you to the father, but Jesus himself. Even the priests in the temple who had all the trappings of piety have no idea who God is because they do not accept Jesus.
21 Once more Jesus said to them, "I am going away, and you will look for me, and you will die in your sin. Where I go, you cannot come."
22 This made the Jews ask, "Will he kill himself? Is that why he says, 'Where I go, you cannot come'?"
23 But he continued, "You are from below; I am from above. You are of this world; I am not of this world. 24 I told you that you would die in your sins; if you do not believe that I am the one I claim to be, you will indeed die in your sins."
25 "Who are you?" they asked.
"Just what I have been claiming all along," Jesus replied. 26 "I have much to say in judgment of you. But he who sent me is reliable, and what I have heard from him I tell the world."
There is a very real judgment coming, which we, like Jesus, are to tell the world. If you do not believe that Jesus is the Messiah, you will die in your sins.
27 They did not understand that he was telling them about his Father. 28 So Jesus said, "When you have lifted up the Son of Man, then you will know that I am the one I claim to be and that I do nothing on my own but speak just what the Father has taught me. 29 The one who sent me is with me; he has not left me alone, for I always do what pleases him." 30 Even as he spoke, many put their faith in him.
Jesus is referring to his death on the cross here when he speaks of being lifted up. Many people realized that when it happened and had one of two reactions. These are the same reactions that you can choose from today when hearing the gospel. You can either reject Him or put your faith in Him.