“A strange peculiarity has been noticed about Hermon, in the extreme rapidity of the formation of cloud on the summit. In a few minutes a thick cap forms over the top of the mountain, and as quickly disperses and entirely disappears” (Edersheim).
Overshadowed them (ἐπεσκίαζεν)
A beautiful imperfect: “began to overshadow them;” thus harmonizing with the words, “as they entered into.” Them (αὐτοὺς) must, I think, be confined to Moses, Elias, and Jesus. Grammatically, it might include all the six; but the disciples hear the voice out of the cloud, and the cloud, as a symbol of the divine presence, rests on these three as a sign to the disciples. See Exo 14:19; Exo 19:16; 1Ki 8:10; Psa 104:3.