Exodus 19:17

15He said to the people, “Be ready by the third day. Don’t have sexual relations with a woman.”

16On the third day, when it was morning, there were thunders and lightnings, and a thick cloud on the mountain, and the sound of an exceedingly loud trumpet; and all the people who were in the camp trembled.

17Moses led the people out of the camp to meet God; and they stood at the lower part of the mountain.

18All of Mount Sinai smoked, because the LORD descended on it in fire; and its smoke ascended like the smoke of a furnace, and the whole mountain quaked greatly.

19When the sound of the trumpet grew louder and louder, Moses spoke, and God answered him by a voice.