Exodus 19:16-22

On the morning of the third day there was thunder and lightning, as well as a thick cloud on the mountain, and a blast of a trumpet so loud that all the people who were in the camp trembled. Moses brought the people out of the camp to meet God. They took their stand at the foot of the mountain. Now Mount Sinai was wrapped in smoke, because the LORD had descended upon it in fire; the smoke went up like the smoke of a kiln, while the whole mountain shook violently. As the blast of the trumpet grew louder and louder, Moses would speak and God would answer him in thunder. When the LORD descended upon Mount Sinai, to the top of the mountain, the LORD summoned Moses to the top of the mountain, and Moses went up. Then the LORD said to Moses, “Go down and warn the people not to break through to the LORD to look; otherwise many of them will perish. Even the priests who approach the LORD must consecrate themselves or the LORD will break out against them.”