Exodus 19:20-22

When the LORD came down on top of Mount Sinai, he called Moses to come up to the top of the mountain, and Moses went up. The LORD said to Moses, “Go down and warn the people that they must not force their way through to see me. If they do, many of them will die. Even the priests, who may come near me, must first prepare themselves. If they don’t, I, the LORD, will punish them.”