Then the sign of the Son of man will appear in heaven, and all the peoples of the earth will mourn. They will see the Son of man coming on the clouds of heaven with power and in brilliant glory.
This is why the saying spread among the believers that this disciple would not die. But Jesus didn't say to him that he wouldn't die, just that “If I want him to remain alive here until I return, why is that your concern?”
But we see Jesus, for a little while placed a little lower than the angels, through the suffering of death crowned with glory and honor. Through God's grace Jesus experienced death for everyone.