Exodus 19:21-24

21Then Adonai said to Moses, “Go down and warn the people, lest they break through to see Adonai, and many of them die.

22Even the kohanim who come near to Adonai must consecrate themselves, so that Adonai does not break out against them.”

23Moses said to Adonai, “The people cannot come up to Mount Sinai, for You are the One who warned us, saying, ‘Set boundaries around the mountain, and consecrate it.’”

24Then Adonai said to him, “Go down. You are to come back up, you and Aaron with you. But do not let the kohanim and the people break through to come up to Adonai, or He will break out against them.”