John 21:23

Ἐξῆλθεν … πρός σε; “There went forth this saying among the brethren, that that disciple should not die”. John himself, however, has no such belief, because he remembers with exactness the hypothetical form of the Lord's words, Ἐὰν αὐτὸν θέλω μένειν … Another instance of the precision with which John recalled some, at least, of the words of Jesus.

In John 21:24, the writer of the gospel is identified with the disciple whom Jesus loved, and a certificate of his truth is added. The whole verse has a strong resemblance to John 19:35, and it seems impossible to say with certainty whether they were or were not written by the evangelist himself. The οἴδαμεν might seem to imply that several united in this certificate. But who in John's old age were there, who could so certify the truth of the gospel? They could have no personal, direct knowledge of the facts; and could merely affirm the habitual truthfulness of John. Cf. too the οἶμαι of John 21:25 where a return to the singular is made; but this may be because in the former clause the writer speaks in the name of several others, while in the latter he speaks in his own name. Who these others were, disciples, Ephesian presbyters, friends, Apostles, it is vain to conjecture. τούτων and ταῦτα refer to the whole gospel, including chap. 21. Besides the things narrated ἔστι δὲ … Ἀμήν. The verse re-affirms the statement of John 20:30, adding a hyperbolical estimate of the space required to recount all that Jesus did, if each detail were separately told, ἐὰν γράφηται καθʼ ἕν.