Exodus 19:10-13

10Then the LORD said to Moses, “Go to the people and consecrate them today and tomorrow. They must wash their clothes 11and be prepared by the third day, for on the third day the LORD will come down on Mount Sinai in the sight of all the people.

12And you are to set up a boundary for the people around the mountain and tell them, ‘Be careful not to go up on the mountain or touch its base. Whoever touches the mountain shall surely be put to death. 13No hand shall touch him, but he shall surely be stoned or shot with arrows—whether man or beast, he must not live.’1

Only when the ram’s horn sounds a long blast may they approach the mountain.2”