Exodus 19:18-20

Now Mount Sinai was completely in smoke, because the LORD descended upon it in fire. Its smoke ascended like the smoke of a furnace, and the whole mountain quaked greatly. And when the blast of the trumpet sounded long and became louder and louder, Moses spoke, and God answered him by voice. Then the LORD came down upon Mount Sinai, on the top of the mountain. And the LORD called Moses to the top of the mountain, and Moses went up.