Exodus 19:16-18

On the morning of the third day, thunder roared and lightning flashed, and a dense cloud came down on the mountain. There was a long, loud blast from a ram’s horn, and all the people trembled. Moses led them out from the camp to meet with God, and they stood at the foot of the mountain. All of Mount Sinai was covered with smoke because the LORD had descended on it in the form of fire. The smoke billowed into the sky like smoke from a brick kiln, and the whole mountain shook violently.