Exodus 19:9 - Clarke's commentary and critical notes on the Bible

And the LORD said unto Moses, Lo, I come unto thee in a thick cloud, that the people may hear when I speak with thee, and believe thee for ever. And Moses told the words of the people unto the LORD. A thick cloud - This is interpreted by Exodus 19:18 : And Mount Sinai was altogether on a Smoke - and the Smoke thereof ascended as the Smoke of a furnace; his usual appearance was in the cloudy pillar, which we may suppose was generally clear and luminous. That the people may hear - See Clarke's note on Exodus 15:9. The Jews consider this as the fullest evidence their fathers had of the Divine mission of Moses; themselves were permitted to see this awfully glorious sight, and to hear God himself speak out of the thick darkness: for before this, as Rabbi Maymon remarks, they might have thought that Moses wrought his miracles by sorcery or enchantment; but now, hearing the voice of God himself, they could no longer disbelieve nor even doubt.