Exodus 19:11-12
Exodus 19:11-12 ASV
and be ready against the third day; for the third day Jehovah will come down in the sight of all the people upon mount Sinai. And thou shalt set bounds unto the people round about, saying, Take heed to yourselves, that ye go not up into the mount, or touch the border of it: whosoever toucheth the mount shall be surely put to death