Exodus 19:10-12

Amplified Bible

¹⁰ The Lord also said to Moses, “Go to the people and consecrate them today and tomorrow [that is, prepare them for My sacred purpose], and have them wash their clothes ¹¹ and be ready by the third day, because on the third day the Lord will come down on Mount Sinai [in the cloud] in the sight of all the people. ¹² You shall set barriers for the people all around [the mountain], saying, ‘Beware that you do not go up on the mountain or touch its border; whoever touches the mountain must be put to death.