Exodus 19:10-12

10The Lord also said to Moses, “Go to the people and 1consecrate them today and tomorrow, and let them 2wash their garments;

11and let them be ready for the third day, for on 3the third day the Lord will come down on Mount Sinai in the sight of all the people.

12You shall set bounds for the people all around, saying, ‘4Beware that you do not go up on the mountain or touch the border of it; 5whoever touches the mountain shall surely be put to death.