Tertullian and the appendix of the gospel of John.
John 20.30-31 and 21.25.
Tertullian, in his work Against Praxeas, has an interesting statement about the conclusion of the gospel of John. Praxeas, his doctrinal opponent in this work, claims that Jesus Christ is the father, and that there is thus no separation of persons in the godhead.
Tertullian, after rehearsing the general catholic doctrine of father and son in chapters 1-19, begins in chapter 20 to address the prooftexts of the Praxean position. Tertullian maintains that there are three:
Of these, Tertullian appears to regard John 14.9-10 as the principal text.
So in chapters 21-23 he runs carefully through the gospel of John up to that point, in order, especially remarking on John 10.30, of course. Chapter 24, then, is dedicated entirely to a close exposition of John 14.9-10 itself. He summons other passages to his aid, of course, but concentrates on the text at hand.
What is important for us here is that Tertullian clearly has a copy of John open before him. His references are too dense, too exact, and too much in order to suppose otherwise.
Chapter 25 then opens up:
He then discusses a handful of texts from after John 14.9-10, and turns to write in the rest of the chapter about the distinction between the father and the son in the resurrection account of the fourth gospel. He has just quoted John 20.17, about Jesus ascending to the father, when in 25.4 he writes:
Tertullian informs us, then, that the clausula (the conclusion) of the fourth gospel says (inquit) something about believing that Jesus is the son of God. But that is not what John 21.25, the conclusion of our current book of John, has to say. Nothing in chapter 21 of the fourth gospel says anything like that. It is John 20.30-31 that tells us that the gospel was written so that we might believe:
There is no use supposing that Tertullian is merely quoting from memory, and has slurred John 20.30-31 with 21.25. He has demonstrated in chapters 21-25 that he has a copy of John before him, and is quoting from it. And he has just finished quoting John 20.17 exactly. (He even interrupts himself in the middle of that verse to make a comment about the implications of Jesus calling the disciples his brethren before picking up the verse right where he left off and finishing it.)
It looks very much like Tertullian had a copy of the fourth gospel that concluded with 20.30-31, lacking chapter 21 entirely.
On the other hand, Tertullian is well aware of the ancient rumor that one of the disciples was expected to live until the advent of the Lord. From Concerning the Soul 50.5:
This misguided hope, of course, is the topic of a passage toward the end of the Johannine appendix, John 21.20-23, in which it it affirmed that some of the brethren supposed that the beloved disciple would remain till the coming of Jesus, and thus not die. I cite only the last verse:
It seems quite doubtful to me that an oral tradition of this frustrated hope survived to the time of Tertullian (who flourished in about the year 200). This passage of his, therefore, is evidence that Tertullian did know the Johannine appendix after all. Did he know it as the conclusion of the gospel? Did the appendix float around separately in some areas? Was there another document, now lost to us, that mentioned this early rumor?