Exodus 19:18-21

18Mount Sinai was covered with smoke, because the Lord descended on it in fire. The smoke billowed up from it like smoke from a furnace, and the whole mountain trembled violently.

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

20The Lord descended to the top of Mount Sinai and called Moses to the top of the mountain. So Moses went up

21and the Lord said to him, “Go down and warn the people so they do not force their way through to see the Lord and many of them perish.