Exodus 19:13-19

13There shall not an hand touch it, but he shall surely be stoned, or shot through; whether it be beast or man, it shall not live: when the trumpet soundeth long, they shall come up to the mount.1 14And Moses went down from the mount to the people, and sanctified the people; and they washed their clothes. 15And he said to the people, Be ready for the third day: come not at your 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 were in the camp trembled. 17And Moses brought forth the people out of the camp to meet with God; and they stood at the lower part of the mount. 18And mount Sinai was altogether in a smoke, because the LORD descended upon it in fire: and the smoke of it ascended as the smoke of a furnace, and the whole mount trembled greatly. 19And when the voice of the trumpet sounded long, and grew louder and louder, Moses spoke, and God answered him by a voice.