Exodus 19:20-22

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. And the LORD said to Moses, “Go down and warn the people, lest they break through to gaze at the LORD, and many of them perish. Also let the priests who come near the LORD consecrate themselves, lest the LORD break out against them.”