Exodus 19:17KJV

15And he said unto the people, Be ready against the third day: come not at wives.

16And it came to pass on the third day in the morning, that there were thunders and lightnings, and a thick cloud upon the mount, and the voice of the trumpet exceeding loud; so that all the people that in the camp trembled.

17And Moses brought forth the people out of the camp to meet with God; and they stood at the nether part of the mount.

18And mount Sinai was altogether on a smoke, because the LORD descended upon it in fire: and the smoke thereof ascended as the smoke of a furnace, and the whole mount quaked greatly.

19And when the voice of the trumpet sounded long, and waxed louder and louder, Moses spake, and God answered him by a voice.