30 I can of mine own self do nothing: as I hear, I judge: and my judgment is just; because I seek not mine own will, but the will of the Father which hath sent me.

[I can of mine own self do nothing] Because of my intimate union with God. See verse 19.

[As I hear, I judge: and my judgement is just] I know God's will because I am party to it. I teach it to you now and will eventually judge you by it.
God's will is in our best intrest because he is omniscient (all knowing), infallible, loves us, and seeks that which is best for us. His ultimate evaluation will also be just, which means he will not be swayed by emotion or reputation or popular opinion. The single-question test at the end of life is already known, What is your relationship with Jesus? John 3:16-18.

[I seek not mine own will] I do not, I cannot attempt to do anything apart from God. This human nature in which I have wrapped myself, John 1:14, is perfectly subject to the Diety that dwells in it. In this respect our blessed Lord is the perfect pattern for all of his followers. In every thing their wills should submit to the will of the Heavenly Father. Nothing is more common than to hear people say, "I will do it because I choose." He who has no better reason to give for his conduct than his own will shall in the end have the same reason to give for his eternal destruction. "I followed my own will, in opposition to the will of God, and now I am plunged into the lake that burns with fire and brimstone."

31 If I bear witness of myself, my witness is not true.

[If I bear witness] If I had no proof to bring of my being the Messiah, and equal to God, common sense would direct you to reject my testimony.

32 There is another that beareth witness of me; and I know that the witness which he witnesseth of me is true.
33 Ye sent unto John, and he bare witness unto the truth.

[Ye sent unto John] I am not without testimony of the most respectable kind; - you sent to John and he was my witness. There are several circumstances which render the testimony of John believable. (1) He is counted, even by the enemies of Christ, as a very holy and extraordinary man. (2) He is perfectly free from all self interest, having declined taking the least advantage from his own reputation. (3) He is sincere, undaunted and so averse to all kinds of flattery that he reproves Herod at the hazard of his liberty and life. (4) He was so far from being solicited by Christ to give his testimony that he had not even seen him when he first gave it.

34 But I receive not testimony from man: but these things I say, that ye might be saved.
35 He was a burning and a shining light: and ye were willing for a season to rejoice in his light.

[I receive not testimony from man] I have no need of John's testimony but I point you to it that YOU might be saved. He was a clear and steady lamp, illuminating "The Lamb of God which taketh away the sin of the world." He was more than a prophet because he pointed out, not the messiah who was to come, but the messiah who was already come.

36 But I have greater witness than that of John: for the works which the Father hath given me to finish, the same works that I do, bear witness of me, that the Father hath sent me.

[But I have a greater witness] I am not obliged to depend upon his testimony alone; for I have a greater one; that of Him whom you acknowledge to be your God. And how do I prove that this God bears testimony to me? By my works; these miracles which attest to my mission, and prove by themselves that nothing less than unlimited power and boundless love could ever produce them. By my word only I have perfectly and instantly healed a man who was diseased thirty eight years. Ye see the miracle - the man is before you whole and sound.

37 And the Father himself, which hath sent me, hath borne witness of me. Ye have neither heard his voice at any time, nor seen his shape.

[The Father himself... hath born witness of me] Not that God the Father ever appeared visibly or spake audible to any of you, but, by his Spirit in your prophets, described my person, office and miracles. You read these scriptures and you cannot help seeing that they testify of me; - no person ever did answer the description there given, but myself, and I answer to that description in the fullest sense of the word.

38 And ye have not his word abiding in you: for whom he hath sent, him ye believe not.

[Ye have not his word abiding in you] Though you believe the Scriptures to be of God, yet you do not let them take hold of your hearts. His word is in your mouth but not on your mind.

39 Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me.

[And ye will not come unto me] Though you thus search the Scriptures in hopes of finding the Messiah and eternal life in them, yet you will not come to me, believe in me, become my disciples, though I am so clearly pointed out by them.

Human nature at work here? When introduced to a celebrity people tend to respond with, " No! It can't be. Is it really you? I don't believe it." and so on. When Peter was in prison the church met to pray for his release. The conversation went something like this: "God, please let Peter be released from Prison." "Excuse me, Mr. Peter is at the door." "It can't be! God, please let Peter out of prison." When they saw it was really Peter they were astonished. Acts 12.

41 I receive not honour from men.

Even today, when people are confronted with Christ, they often filter the information through popular opinions which they have heard all their lives. "God is dead," or "God is a myth" or "God is not relevant to today's society." Imagine the astonishment of some of today's religious leaders and their followers when they discover the truth.

42 But I know you, that ye have not the love of God in you.

[How can ye believe] You are so busy honoring one another, giving and receiving awards and adulation, that you are satisfied with yourselves and feel no need for God's interference in your lives.

45 Do not think that I will accuse you to the Father: there is one that accuseth you, even Moses, in whom ye trust.
46 For had ye believed Moses, ye would have believed me; for he wrote of me.
47 But if ye believe not his writings, how shall ye believe my words?

You have accused me with a breach of the Sabbath, which accusation I have demonstrated to be false. I could, in return, accuse you, and substantiate the accusation, with the breach of the whole law; but this I need not do, for Moses, whom you trust, accuses you. You read the law, acknowledge that you should obey it, and yet break it in both letter and spirit. If you do not believe what Moses wrote of me, how can you believe what I say?