A.T. Robertson Commentary Luke 9:28

"And it came to pass about eight days after these sayings, that he took with him Peter and John and James, and went up into the mountain to pray." — Luke 9:28 (ASV)

About eight days (ωσε ημερα οκτω). A nominativus pendens without connexion or construction. Mr 9:2 (Matthew 17:1) has "after six days" which agrees with the general statement.

Into the mountain (εις το ορος). Probably Mount Hermon because we know that Jesus was near Caesarea Philippi when Peter made the confession (Matthew 16:13). Hermon is still the glory of Palestine from whose heights one can view the whole of the land. It was a fit place for the Transfiguration.

To pray (προσευξασθα). Peculiar to Luke who so often mentions Christ's habit of prayer (cf. 3:21). See also verse 29 "as he was praying" (εν τω προσευχεσθα, one of Luke's favourite idioms).

His countenance was altered (εγενετο το ειδος του προσωπου αυτου ετερον). Literally, "the appearance of his face became different."Matthew 17:2 says that "his face did shine as the sun." Luke does not use the word "transfigured" (μετεμορφωθη) in Mr 9:2; Matthew 17:2. He may have avoided this word because of the pagan associations with this word as Ovid's Μεταμορφοσες.

And his raiment became white and dazzling (κα ο ιματισμος αυτου λευκος εξαστραπτων). Literally,

And his raiment white radiant . There is no and between "white" and "dazzling." The participle εξαστραπτων is from the compound verb meaning to flash (αστραπτω) out or forth (εξ). The simple verb is common for lightning flashes and bolts, but the compound in the LXX and here alone in the N.T. See Mr 9:3 "exceeding white" and Mt 17:2 "white as the light."