Albert Barnes Commentary Matthew 17:5

"While he was yet speaking, behold, a bright cloud overshadowed them: and behold, a voice out of the cloud, saying, This is my beloved Son, in whom I am well pleased; hear ye him." — Matthew 17:5 (ASV)

A bright cloud overshadowed them. The word overshadow here means, rather, to be diffused or spread over them. It does not mean that it made a shade.

A cloud was a symbol of the Divine Presence. Thus God went before the Israelites in a cloudy pillar—dark by day and bright by night (Exodus 14:19–20). He appeared on Mount Sinai in a cloud bright by fire (Exodus 24:15–17), and a cloud, the symbol of the Divine Presence—called the Shechinah—dwelt continually in the Most Holy Place in the temple (1 Kings 8:10–11; Ezekiel 1:4; Ezekiel 10:4).

When, therefore, the disciples saw this cloud, they were prepared to hear the word of the Lord.

This is my beloved Son. This was the voice of God. This was the second time that, in a remarkable manner, he had declared this. See Matthew 3:17.

This was spoken to confirm the disciples; to declare their duty to hear Christ rather than any other, and to honour him more than Moses and Elijah; and to strengthen their faith in him when they should go forth to preach the gospel, after he was shamefully put to death. After this, it was impossible for them to doubt that he was truly the Son of God. See 2 Peter 1:17–18.

• in whom: Isaiah 42:1, 21
• hear ye: Deuteronomy 18:15, 19; Acts 3:22–23; Hebrews 1:1–2; Hebrews 2:1–3