John 21:23

This saying therefore went forth among the brethren, that that disciple should not die: yet Jesus said not unto him, that he should not die; but, If I will that he tarry till I come, what is that to thee?

Thus, John laid to rest the tradition that had developed to the effect that the Lord would return in John's lifetime (the propositions being equivalent). At the time he wrote John, the apostle was very old; and it was apparent to him and others that the days of his pilgrimage were drawing to a close; and, in view of the probable event of his death, he did not wish unbelievers to have an excuse for saying that the prophecy of the Lord had failed. He therefore made it clear that no such prophecy had ever been uttered.