William Burkitt on John 21:23

Observe here, how strangely our Saviour's words were mistaken and misunderstood by his own disciples; they apprehend presently that John should not die, and so it passed current among them.

From hence we may note, how much the wisdom of God is, and ought to be admired, in giving us a written word, and tying us to it, when we see erroneous traditions so soon on foot in the world, and our Saviour's own speeches so much mistaken, and that by wise and holy men themselves in the purest times. Much more may the words of others be misreported, and wrested contrary to their sense and meaning. How great then is the vanity and uncertainty of oral tradition! Men are naturally prone to mistake, to mistake themselves, and to mistake one another. The more to be admired is their over-daring ignorance, who think they cannot err. Such a haughty opinion of a man's self, concludes him to be neither good nor wise.