Exodus 19:16-18 - WEB
16
It happened on the third day, when it was morning, that 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.
17
Moses led the people out of the camp to meet God; and they stood at the lower part of the mountain.
18
Mount Sinai, the whole of it, smoked, because Yahweh descended on it in fire; and its smoke ascended like the smoke of a furnace, and the whole mountain quaked greatly.
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