Exodus 19:16-22

16And it came to pass on the third day, when it was morning, that there were thunders and lightnings, and a thick cloud upon the mount, and the voice of a trumpet exceeding loud; and all the people that were in the camp trembled. 17And Moses brought forth the people out of the camp to meet God; and they stood at the nether part of the mount. 18And mount Sinai, the whole of it, smoked, because Jehovah 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 waxed louder and louder, Moses spake, and God answered him by a voice. 20And Jehovah came down upon mount Sinai, to the top of the mount: and Jehovah called Moses to the top of the mount; and Moses went up. 21And Jehovah said unto Moses, Go down, charge the people, lest they break through unto Jehovah to gaze, and many of them perish. 22And let the priests also, that come near to Jehovah, sanctify themselves, lest Jehovah break forth upon them.