John 19. 35-37
35 The one having seen it has given testimony, and his testimony is true, and he knows that what he says is true, that you all might believe.
36 For these things happened so that the Scripture might be fulfilled: “Not one bone of His will be crushed”.
37 Also another Scripture says; “They will look on the One they have pierced.”
It would seem that John was aware that there were those within the early church who were casting doubts on the suffering of Jesus. We have seen that these were the Gnostics who had infiltrated the church and they denied the physical suffering of Jesus, and also they denied that Jesus had a physical body. They believed that He could not have had a physical body because a physical body is matter, and they believed that matter was evil.
Therefore, John is keen to emphasize the physical nature of the sufferings of Jesus. He does this by stating that he was there, and that he knows that what he saw was true.
He wrote his gospel, under the guidance of the Holy Spirit, to state the truth of the reality of Jesus being crucified.
His was a first-hand account of what happened. This was in contrast from the theories of the Gnostics, who were not there, but who tried to make the events fit their heretical theories.
A first-hand witness account is a tremendous asset. Someone who can say that they were a witness to something has a great advantage over those who were not. A first-hand witness is able to say: “I was there. I saw what happened.”
John was able to say this. It is his testimony that he was there at the cross, along with the women. They all saw the agony and suffering that Jesus went through.
John may have been writing some sixty years later, but his memory has not dimmed. The events of the crucifixion of Jesus were still very vivid in his memory. This is not surprising since the crucifixion and resurrection changed the course of human history. John was able to say that he witnessed this.
Every born again believer has a first-hand account of meeting with Jesus. How we came to know Him is forever imprinted on our mind. Nobody can take that memory and experience from us. It is unique. If you have not already done so, it would be a good idea to write down your experience of meeting with Jesus, so that others, especially the next generation can read of the power of Jesus to change your life.