Exodus 19:20

Moses led the people out of the camp to meet God; and they stood at the lower part of the mountain.

All of Mount Sinai smoked, because the LORD descended on it in fire; and its smoke ascended like the smoke of a furnace, and the whole mountain quaked greatly.

When the sound of the trumpet grew louder and louder, Moses spoke, and God answered him by a voice.

The LORD said to Moses, “Go down, warn the people, lest they break through to the LORD to gaze, and many of them perish.

Let the priests also, who come near to the LORD, sanctify themselves, lest the LORD break out on them.”

Moses said to the LORD, “The people can’t come up to Mount Sinai, for you warned us, saying, ‘Set bounds around the mountain, and sanctify it.’”