16. On the morning of the third day there were thunders and lightnings and a thick cloud on the mountain and a very loud trumpet blast, so that all the people in the camp trembled.
17. Then Moses brought the people out of the camp to meet God, and they took their stand at the foot of the mountain.
18. Now Mount Sinai was wrapped in smoke because the LORD had descended on it in fire. The smoke of it went up like the smoke of a kiln, and the whole mountain trembled greatly.
19. And as the sound of the trumpet grew louder and louder, Moses spoke, and God answered him in thunder.
20. 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 Moses went up.

Exodus 20

18. Now when all the people saw the thunder and the flashes of lightning and the sound of the trumpet and the mountain smoking, the people were afraid and trembled, and they stood far off
19. and said to Moses, “You speak to us, and we will listen; but do not let God speak to us, lest we die.”
20. Moses said to the people, “Do not fear, for God has come to test you, that the fear of him may be before you, that you may not sin.”
21. The people stood far off, while Moses drew near to the thick darkness where God was.

ESV