This is that disciple. Having hitherto mentioned himself in the third person, John now declares that it is himself; that greater weight may be attached to the statements of one who was an eye-witness, and who had fully known all that he relates.

This is the disciple - This proves that the beloved disciple was John.
We know - That is, it is known; it is universally admitted. It was so decidedly his character that he always declared the truth, that it had become known and was unquestioned, so that he himself might appeal to the universal testimony in his behalf. In this case, therefore, we have the testimony of a man whose character for nearly a century was that of a man of truth - so much so that it had become, in a manner, proverbial, and was put beyond a doubt. It is impossible to believe that such a man would sit down deliberately to impose on mankind, or to write a book which was false; and if not, then this book is true, and that is the same as saying that Christianity is a religion from heaven.

This is the disciple - It is, I think, very likely that these two verses were added by some of the believers at that time, as a testimony to the truth of the preceding narration; and I allow, with Bishop Pearce and others, that it is possible that John may mean himself when he says We know, etc., yet, I think that it is very unlikely. It is certain that this Gospel loses no part of its authority in admitting the suffrage of the Church of God: it rather strengthens the important truths which are delivered in it; and in the mouths of so many witnesses the sacred matters which concern the peace and salvation of the world, are still more abundantly established. See the last note on the preceding chapter.
We know - Instead of οιδαμεν, we know, some have written οιδα μεν, I know indeed; but this is mere conjecture, and is worthy of no regard. It is likely that these verses were added by those to whom John gave his work in charge.

(5) This is the disciple which testifieth of these things, and wrote these things: and we know that his testimony is true.
(5) The history of Christ is truly and cautiously written: not for the curiosity of men, but for the salvation of the godly.

This is the disciple which testifieth of these things,.... Recorded in this chapter concerning the appearance of Christ to his disciples at the sea of Tiberias, and what were done by him in their presence, what passed between them; particularly the conversation he had with Peter, both concerning himself, and the disciple John: and also, of all things that are written in this whole Gospel. These are testified to be true by this very disciple John, concerning whom the above report went upon a mistaken sense of Christ's words, and who himself
wrote these things; all that is contained in this book, as well as the particulars relating to this conversation of Christ with Peter:
and we know that his testimony is true. The testimony of one that was an eye and ear-witness, as John was, of all that he testified and wrote, must be known, owned, and allowed by all to be true, firm, and unquestionable; and therefore the apostle speaks in the plural number, as being not only his own sense, but the sense of all men. Though some take this to be the attestation of the Ephesian church, or of the bishops of the Asiatic churches, who put John upon writing this Gospel; of which they give their judgment and testimony, as believing it to be a true and faithful narrative.

FINAL CLOSE OF THIS GOSPEL. (John 21:24-25)
This is the disciple which testifieth of these things, and wrote these things--thus identifying the author of this book with all that it says of this disciple.
we know that his testimony is true--(Compare John 19:35).

We know that his testimony is true. Many suppose the last two verses were added by another hand than John's, perhaps by the elders of the church at Ephesus, where John wrote, who give their endorsement to his record.
I suppose. An opinion of the endorsers, or rather a hyperbole. It is added to show how little comparatively of the words and works of that wonderful life have been recorded.

This is the disciple who testifieth - Being still alive after he had wrote. And we know that his testimony is true - The Church added these words to St. John's, Gospel, as Tertius did those to St. Paul's Epistle to the Romans, Romans 16:22.