|This word [truth] is one of the dominant notes of the Fourth Gospel. We meet it again and again. Here we can only briefly gather together what John has to say about Jesus and the truth.
(a) Jesus is the embodiment of the truth. He said: "I am the truth." (Jn 14:6 ) To see truth we must look at Jesus. Here is something infinitely precious for every simple mind and soul. Very few people can grasp abstract ideas; most people think in pictures. We could think and argue for ever and we would very likely be no nearer arriving at a definition of beauty. But if we can point at a beautiful person and say that is beauty, the thing becomes clear. Ever since men began to think about God they have been trying to define just who and what he is — and their puny minds get no nearer a definition. But we can cease our thinking and look at Jesus Christ and say: "That is what God is like." Jesus did not come to talk to men about God; he came to show men what God is like, so that the simplest mind might know him as intimately as the mind of the greatest philosopher.
(b) Jesus is the communicator of the truth. He told his disciples that if they continued with him they would know the truth. (Jn 8:31 ) he told Pilate that his object in coming into this world was to witness to the truth. (Jn 18:37 ) Men will flock to a teacher or preacher who can really give them guidance for the tangled business of thinking and living. Jesus is the one who, amidst the shadows, makes things clear; who, at the many crossroads of life, shows us the right way; who, in the baffling moments of decision, enables us to choose aright; who, amidst the many voices which clamour for our allegiance, tells us what to believe.
(c) Even when Jesus left this earth in the body, he left us his Spirit to guide us into the truth. His Spirit is the Spirit of truth. (Jn 14:17; 15:26; 16:13 ) he did not leave us only a book of instruction and a body of teaching. We do not need to search through some unintelligible textbook to find out what to do. Still, to this day, we can ask Jesus what to do, for his Spirit is with us every step of the way.
(d) The truth is what makes us free. (Jn 8:32 ) There is always a certain liberating quality in the truth. A child often gets queer, mistaken notions about things when he thinks about them himself; and often he becomes afraid. When he is told the truth he is emancipated from his fears. A man may fear that he is ill; he goes to the doctor; even if the verdict is bad he is at least liberated from the vague fears which haunted his mind. The truth which Jesus brings liberates us from estrangement from God; it liberates us from frustration; it liberates us from our fears and weaknesses and defeats. Jesus Christ is the greatest liberator on earth.
(e) The truth can be resented. They sought to kill Jesus because he told them the truth. (Jn 8:40 ) The truth may well condemn a man; it may well show him how far wrong he was. "Truth," said the Cynics, "can be like the light to sore eyes." The Cynics declared that the teacher who never annoyed anyone never did anyone any good. Men may shut their ears and their minds to the truth; they may kill the man who tens them the truth — but the truth remains. No man ever destroyed the truth by refusing to listen to the voice that told it to him; and the truth will always catch up with him in the end.
(f) The truth can be disbelieved. (Jn 8:45 ) There are two main reasons why men disbelieve the truth. They may disbelieve it because it seems too good to be true; or they may disbelieve it because they are so fastened to their half-truths that they will not let them go. In many instances a half-truth is the worst enemy of a whole truth.
(g) The truth is not something abstract; it is something which must be done. (Jn 3:21 ) It is something which must be known with the mind, accepted with the heart, and acted out in the life.
(Barclay, Daily Study Bible)