[They said this] so that the words Jesus had spoken would be fulfilled, regarding the kind of death He would die. [Note: Jesus had predicted he would be “lifted up,” indicating a Roman crucifixion. See 12:32-33].
Now Jesus said this to indicate the kind of death Peter would experience in honoring God. [Note: Some see the “stretching out your hands,” verse 18, as a reference to crucifixion]. And after saying this, Jesus said to him, “Be my follower.”