Exodus 19:10-13

10And Jehovah said to Moses, Go to the people, and hallow them to-day and to-morrow, and let them wash their clothes;

11and let them be ready for the third day; for on the third day Jehovah will come down before the eyes of all the people on mount Sinai.

12And set bounds round about the people, saying, Take heed to yourselves, [not] to go up unto the mountain nor touch the border of it: whatever toucheth the mountain shall certainly be put to death:

13not a hand shall touch it, but it shall certainly be stoned, or shot through; whether it be a beast or a man, it shall not live. When the long drawn note of the trumpet soundeth, they shall come up to the mountain.