Summary: All of John's gospel was written for this purpose
That You Might Believe
John 20:30-31 and 21:24-25
Today we are finishing up our long study of the Gospel of John. We will include a text from the 20th chapter that we skipped over because it goes well with the last two verses of the 21st chapter. John almost seems to end the Gospel at 20:30-31 which is the purpose of the entire book. But then he goes on in the same way Paul seems to end Romans, and then proceeds to go on further. The fishing trip looks in this view like John having concluded at the 20th chapter is reminded of this one final incident he feels compelled to add. For this we are eternally thankful.
But after the fishing trip, John realizes that he could write forever about what Jesus had done or said. He supposes the things he could have recorded would have more than filled all of earth itself. So John, having added one more important incident in the life of Jesus, brings the entire gospel to a close.
I would like to zero in more on the first ending of the Gospel of John. Logically, this needs to be discussed at the end of John.
Exposition of the Text
The first ending is similar to the second. In 20:30, John tells us that there were many other signs which Jesus did in the presence of His disciples that he did not include in his Gospel. This does not mean that the other signs were not important. Indeed, many of them were written in the other gospels. We believe that the Holy Spirit is the author of all Scripture, even though He uses human agents like John. This means that the Spirit inspired which seven signs would be included in this Gospel to stand for the rest. This postscript is just to remind us that the signs are representative and not nearly exhaustive. The selection of these particular signs are sufficient for us to get an understanding of the person, teaching, and work of Jesus Christ.
The same Holy Spirit also inspired the other gospel writers as to what material they should include in their gospels. There is no reason to speculate which gospel might have been a source of the other. Even if this was done as Luke suggests, it is still the work of the Holy Spirit. The other three gospels are more similar. They are three witnesses required by law to establish testimony. However, lest someone say that one copied from the other, the Spirit inspired John to write the fourth gospel, including some similar material as well as much that is not included. This acts as an independent witness to the facts.
Remember when we discussed valid courtroom testimony several chapters back. There I suggested that valid testimony is not word for word identical. If all the events were identically described, it would be the opposite. The opposition could claim that the testimony was rehearsed and copied. This type of testimony would certainly be thrown out in court. Valid testimony comes from different perspectives. What makes it valid is precisely that the testimony is not identical but that it agrees in the major premise. In the case of the resurrection, we see some confusion as to how many women there were and when and other such detail. What makes the testimony valid is that they all testify that Jesus had risen from the dead and proved it on several occasions. The tomb was empty. And so forth.
John states the reason he wrote the Gospel was that all who read it might believe that Jesus is the Christ and that by believing he or she might have (eternal) life in His name or authority. This answers the verse at the beginning of the Gospel in 1:12 which is the central statement in the prologue that to the believers He gave authority to become the children of God. Everything between that verse and this one is a testimony and sign to the truth of the assertion.
John introduced many people to us in this Gospel. The most prominent of course is the witness of Jesus Christ Himself. He by these signs witnessed to Israel and by extension to all who have read the Gospel of John to the Fact He came from the Father to do and teach what He was sent to. But John vividly uses the other people in the gospel to show how the word of Christ worked in them. Some like Nathaniel and the Samaritan woman seemed to have come to faith by a single act of witness to Jesus. We have also followed others whose journey to faith developed over time such as Simon Peter, Thomas, and Nicodemus. We have seen the witness of John the Baptist which was a faithful to Jesus in every respect from the beginning of the Gospel to his death, being a faithful witness even after he was dead. We have seen the testimony of the disciple whom Jesus loved, who was seen through the eyes of Jesus, not for what others would see of him, but in Christ himself who transforms our past and rewrites our lives.