Exodus 19:21-25

21Then the Lord told Moses, “Go back down and warn the people not to break through the boundaries to see the Lord, or they will die.

22Even the priests who regularly come near to the Lord must purify themselves so that the Lord does not break out and destroy them.”

23“But Lord,” Moses protested, “the people cannot come up to Mount Sinai. You already warned us. You told me, ‘Mark off a boundary all around the mountain to set it apart as holy.’”

24But the Lord said, “Go down and bring Aaron back up with you. In the meantime, do not let the priests or the people break through to approach the Lord, or he will break out and destroy them.”

25So Moses went down to the people and told them what the Lord had said.