Exodus 19:11, 18, 20

And let them be ready for the third day. For on the third day the LORD will come down upon Mount Sinai in the sight of all the people.

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.

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.