Albert Barnes Commentary Revelation 6:16

"and they say to the mountains and to the rocks, Fall on us, and hide us from the face of him that sitteth on the throne, and from the wrath of the Lamb:" — Revelation 6:16 (ASV)

And said to the mountains and rocks, Fall on us. This language is found substantially in Hosea 10:8: And they shall say to the mountains, Cover us; and to the hills, Fall on us. It is also used by the Savior as denoting the consternation that would occur at His coming: Then shall they begin to say to the mountains, Fall on us; and to the hills, Cover us (Luke 23:30).

This is language denoting consternation and an awful fear of impending wrath. This state of mind involves an apprehension that God Himself is coming forward with the direct instruments of His vengeance, and reflects a desire to be crushed by falling rocks and hills rather than face the vengeance of His uplifted arm.

From the face of Him that sits on the throne. This refers to the face of God—for He seems to be coming forward with the displays of His vengeance. It is not said that God would actually appear in a visible form, but their consternation would be as great as if He were to do so. The state of mind indicated by this was an apprehension that it would indeed be so.

And from the wrath of the Lamb. This refers to the Lamb of God, the Lord Jesus. See the notes on Revelation 5:6.

There seems to be an incongruity between the words wrath and Lamb; however, the word Lamb here is so much a proper name that it is used only to designate the Redeemer. He comes forward to execute wrath, not as a Lamb, but as the Son of God, who bore that name. It would seem from this that those who thus dreaded the impending terrors were aware of their source, or had knowledge enough to understand by whom they were to be inflicted. They would see that these were Divine judgments, and would apprehend that the end of the world drew near.