Mark 9:7

a cloud not dark and murky, but bright(Matthew 17:5), overshadowed the lawgiver and the prophet, and perhaps also the Lord. "Light in its utmost intensity performs the effects of darkness, hides as effectually as the darkness would do." Comp. 1 Timothy 6:16, and the words of Milton, "dark with excess of light," and of Wordsworth, "a glorious privacy of light." Trench's Studies, pp. 205, 206.

a voice came out of the cloud The same Voice which had been heard once before at the Baptism (Matthew 3:17), and which was to be heard again when He stood on the threshold of His Passion (John 12:28), attesting His Divinity and Sonship at the beginning, at the middle, and at the close of His ministry. Looking back afterwards on the scene now vouchsafed to him and to the "sons of thunder," St Peter speaks of himself and them as "eyewitnesses of His majesty" (2 Peter 1:16), i. e. literally, as men who had been admitted and initiated into secret and holy mysteries, and says that the Voice "came from the excellent glory" (2 Peter 1:17), from Him, that is, Who dwelt in the cloud, which was the symbol and the vehicle of the Divine Presence. St John also clearly alludes to the scene in John 1:14 and 1 John 1:1.

This is my beloved Son "In the words themselves of this majestic installation there is a remarkable honouring of the Old Testament, and of it in all its parts, which can scarcely be regarded as accidental; for the three several clauses of that salutation are drawn severally from the Psalms (Psalms 2:7), the Prophets (Isaiah 42:1), and the Law (Deuteronomy 18:15); and together they proclaim Him, concerning whom they are spoken, to be the King, the Priest, and the Prophet of the New Covenant." Trench, Studies, p. 207.