About eight days later: Mark's Gospel says "after six days," referring to full days. Luke only includes parts of days.
Peter, John, and James were the disciples who were closest to Jesus (see also 8:51; Mark 14:32–33).
a mountain: The traditional site of the transfiguration is Mount Tabor in southern Galilee. Some people think it was Mount Hermon, because it is closer to Caesarea Philippi, where Peter declared that Jesus is the Christ (Luke 9:18–27).