Barnes New Testament Notes

Verse 16. And said to the mountains and rocks, Fall on us, etc.. This language is found substantially in Hos 10:8: "And they shall say to the mountains, Cover us; and to the hills, Fall on us." It is also used by the Saviour as denoting the consternation which would occur at his coming: "Then shall they begin to say to the mountains, Fall on us; and to the hills, Cover us," Lu 23:30. It is language denoting consternation, and an awful fear of impending wrath. The state of mind is that where there is an apprehension that God himself is coming forth with the direct instruments of his vengeance, and where there is a desire rather to be crushed by falling rocks and hills than by the vengeance of his uplifted arm.

From the face of him that sitteth on the throne. The face of God -- for he seems to be coming forth with the displays of his vengeance. It is not said that God would actually come forth in a visible form, but their consternation would be as great as if he were to do this; the state of mind indicated by this was an apprehension that it would be so.

And from the wrath of the Lamb. The Lamb of God; the Lord Jesus. See Barnes on "Re 5:6".

There seems to be an incongruity between the words wrath and Lamb; but the word Lamb here is so far a proper name as to be used only to designate the Redeemer. He comes forth to execute wrath, not as a Lamb, but as the Son of God, who bore that name. It would seem from this that they 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.