Some of the disciples took what Jesus said
to Peter to mean that John would not die,
that he would live until Jesus returned to
the earth.

But John hurried to correct them. He pointed
out that Jesus didn't say that he would not
die, only, that if He willed, John should tarry
until He came.

Rather than saying that John should live
until the actual Second Coming which he
denied was the Lord's meaning; it was that
the world could expect a visit to John from
Jesus.