Mark 9:8
And suddenly, when they had looked round about, they saw no man any more, save Jesus only with themselves.
Cross-reference
Luke 9:36
Parallel
Luke 9:36 is the parallel account of the Transfiguration — after the voice, they see Jesus alone and keep silent, matching the scene here.
Matthew 17:8
Parallel
Matthew 17:8 is the parallel account of the transfiguration — the disciples see only Jesus, same event.
Luke 9:34
Parallel
Luke 9:34 describes the cloud overshadowing them during the same transfiguration event, a preceding moment.