Exodus 19:22-26

Also have the priests who approach the Lord consecrate themselves, or else the Lord will break out against them.”

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

Then the Lord said to him, “Go down and come up again, you and Aaron with you; but do not let the priests and the people break through to come up to the Lord, or He will break out against them.”

So Moses went down to the people and told them.