Adam Clarke on Matthew 17:7

Jesus came and touched them - Exactly parallel to this account is Dan 8:18, I was in a deep sleep, i.e. (a trance) on my face towards the ground; but he Touched me, and set me upright. From Jesus alone are we to expect Divine communications, and by his power only are we able to bear and improve them. It is very likely that this transfiguration took place in the night, which was a more proper season to show forth its glory than the day time, in which a part of the splendor must necessarily be lost by the presence of the solar light. Besides, St. Luke, Luk 9:37, expressly says, that it was on the next day after the transfiguration that our Lord came down from the mount.