Exodus 19:18-20

Mount Sinai was wrapped in smoke because the LORD descended upon it in fire; its smoke ascended like the smoke of a furnace, and the whole mountain quaked violently. And it happened, as the blast of the ram’s horn grew louder and louder, Moses spoke and God answered him with [a voice of] thunder. [Deut 4:12] The LORD came down on Mount Sinai, to the top of the mountain; and the LORD called Moses to the top of the mountain, and he went up.