Jesus answered, “If I honor Myself, My honor is nothing. It is My Father who honors Me, of whom you say that He is your God. Yet you have not known Him, but I know Him. And if I say, ‘I do not know Him,’ I shall be a liar like you; but I do know Him and keep His word. Your father Abraham rejoiced to see My day, and he saw and was glad.” Then the Jews said to Him, “You are not yet fifty years old, and have You seen Abraham?” Jesus said to them, “Most assuredly, I say to you, before Abraham was, I AM.” John 8:54-58
The Gospel according to John was the last of the four gospels, probably written around 90 A.D., and it is very different from Matthew, Mark, and Luke. In his selection of narratives for inclusion in his gospel, John puts to rest any lingering doubts about the divinity of Jesus, or that Jesus was perhaps not the Christ, the Anointed One sent to save His people from their sins. John’s purpose is to make these things clear and undeniable.
In the above passage, Jesus speaks authoritatively that he knows and is known by God the Father, and that He was in existence long before Abraham. These are claims to divinity.
Now read this passage:
So Jesus said to them again, “Peace to you! As the Father has sent Me, I also send you.” And when He had said this, He breathed on them, and said to them, “Receive the Holy Spirit. If you forgive the sins of any, they are forgiven them; if you retain the sins of any, they are retained.” John 20:21-23.
Several times, Christ had claimed to forgive sins (Mat. 9:2; Mark 2:5; Luke 7:48), but here he is deputizing the disciples to forgive sins, saying that what they forgive will be forgiven in heaven, and what they do not forgive will not by forgiven. (See, also, Mat. 18:18) He also states that by merely breathing on them, He can impart the Holy Spirit into them. Here, yet again, Jesus is claiming the prerogatives of God.
This forecloses the idea that Jesus was merely a wise teacher or a good moral example. As C.S. Lewis famously wrote in Mere Christianity:
“I am trying here to prevent anyone saying the really foolish thing that people often say about Him: I’m ready to accept Jesus as a great moral teacher, but I don’t accept his claim to be God. That is the one thing we must not say. A man who was merely a man and said the sort of things Jesus said would not be a great moral teacher. He would either be a lunatic — on the level with the man who says he is a poached egg — or else he would be the Devil of Hell. You must make your choice. Either this man was, and is, the Son of God, or else a madman or something worse. You can shut him up for a fool, you can spit at him and kill him as a demon or you can fall at his feet and call him Lord and God, but let us not come with any patronizing nonsense about his being a great human teacher. He has not left that open to us. He did not intend to.”