The Greek verb diagrēgoreō means to remain thoroughly awake or to keep fully wakeful — staying alert despite drowsiness. It appears only once in the New Testament, in Luke 9:32, where the disciples stayed awake at the Transfiguration and saw Jesus's glory.
The disciples' wakefulness at the Transfiguration is theologically significant. Luke notes they were 'heavy with sleep' but managed to stay awake — unlike the Garden of Gethsemane where they could not keep watch. Their wakefulness was rewarded with one of the most glorious revelations in the Gospels: Moses and Elijah conversing with the transfigured Christ about His coming 'exodus' in Jerusalem. The call to spiritual wakefulness runs throughout the New Testament — 'Keep watch, because you do not know the day or the hour' (Matthew 25:13). The disciples who stayed awake received a foretaste of eschatological glory; the watching church is promised the same.