Exodus 19:16

16.And it came to pass on the third day. We must bear in mind what I have already adverted to, that this terrible spectacle was partly to set the presence of God before their eyes, that His majesty might urge the beholders to obedience, and vindicate His doctrine from contempt, and partly to express the nature of the Law, which in itself produces nothing but mere terror. The air was disturbed by thunder and lightning’s, and the sound of the trumpet; the mountain was wrapped in smoke and darkness, that the people might humbly prostrate themselves before God, and solemnly embrace the covenant proposed to them; since religion never penetrates the mind so that it seriously receives God’s word until its vices are cleansed and corrected, and it is really subdued. And this fear is common also to the Gospel; for as in the promulgation of the Law God shook the earth, so when He speaks by the Prophet of the coming of Christ, and the restoration of His Church, He says, “Yet once, it is a little while, and I will shake the heavens and the earth,” etc. (Haggai 2:6.) Thus, too, David, when he would point to God as the avenger of His Church, describes Him under this image; for no doubt when, in Psalms 18:7, he says, “Then the earth shook and trembled, the foundations also of the hills moved and were shaken, — there went up a smoke out of his nostrils, and fire out of his mouth devoured; he bowed the heavens also, and came down; and darkness was under his feet,” he alludes to the history which Moses here relates. Habakkuk 3:3 yet more plainly does so, — “God came from Teman, and the Holy One from Mount Paran.” Meanwhile the other point remains, that the awful prodigies, at which the people needs must tremble, were added as seals to the promulgation of the Law, because the Law was given to cite slumbering consciences to the judgment-seat, that, through fear of eternal death, they might flee for refuge to God’s mercy.