If chapter 20 is the conclusion of John’s Gospel, and chapter 21 the epilogue, then verses 24-25 can be considered John’s post-script. To this day, when we write letters, we will often use the post-script to remind our readers of something important or to leave them with some impression on their minds. It is John’s intent in his post-script to help the reader penetrate behind the surface of the narrative and incidents recorded, so as to recognize the Eternality of Jesus Christ – the Word made flesh.
Consider that though finite in its pages, the written Word reveals this infinite Word. The magnificence of Scripture is that it infinitely unfolds the deeper we get into it. How could it ever be possible that one can deposit in writing the full significance of all Jesus did? How can the best of expositors be expected to anything but scratch the surface of divine glory? Even should we go word by word devoting an entire study to each verse of Scripture, it is not an exaggeration to say that we would just begin to unearth it. Should one attempt this, he will find that, the world itself could not contain the books that should be written.