Jamieson, Fausset & Brown

and when they were awake--so, certainly, the most commentators: but if we translate literally, it should be "but having kept awake" [MEYER, ALFORD]. Perhaps "having roused themselves up" [OLSHAUSEN] may come near enough to the literal sense; but from the word used we can gather no more than that they shook off their drowsiness. It was night, and the Lord seems to have spent the whole night on the mountain (Luk 9:37). saw his glory, &c.--The emphasis lies on "saw," qualifying them to become "eye-witnesses of His majesty" (Pe2 1:16).