24 This is the disciple who testifies of these things, and wrote these things; and we know that his testimony is true. 25 And there are also many other things that Jesus did, which if they were written one by one, I suppose that even the world itself could not contain the books that would be written. Amen.
John 21:24-25 is a colophon. A colophon is an addition to a piece of writing that gives details about its publication such as the author, the place of writing, or the time when it was written. Here we have information about the composition of the gospel of John. It is an endorsement of John’s credibility in writing the gospel.
This is the disciple [John] who testifies of these things,
John identified himself as the author of this gospel. He owned the fact he was the human source behind the writing of this book.
and wrote these things;
“These things” refers to the entire gospel of John.
and we [John and his community]
The “we” here might be John and the elders of the church in Asia Minor or it might be an editorial we. John wrote down what he saw and heard (John 19:35).
know that his testimony is true.
The Christian community in Asia Minor affirmed the reliability and authenticity of the Holy Spirit using John to write the gospel of John.
And there are also many other things that Jesus did,
None of the gospels gives documentation of everything that Jesus did on earth. God omits from the Bible many things that Jesus did because they are not pertinent to His purpose of divine revelation.
which if they were written one by one, I suppose that even the world itself could not contain the books that would be written.
The “I” here indicates that John was the author of this gospel.
John used hyperbole about the extent of information about Jesus. It appeared to him to be endless.
The word “amen” means so be it. The amen here probably refers to the entire gospel. The entirety of the gospel is true.
Jesus was immeasurably great in His accomplishments.
Jesus’ life left an indelible impression on the world.
There are many questions that are not answered in the Bible, but we have enough revelation to function under God’s will.