Exodus 19:16-20

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 was 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 Yhwh 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. 20And Yhwh came down upon mount Sinai, on the top of the mount: And Yhwh called Moses up to the top of the mount; and Moses went up.