Exodus 19:11-12
Exodus 19:11-12 NASB1995
and let them be ready for the third day, for on the third day the LORD will come down on Mount Sinai in the sight of all the people. You shall set bounds for the people all around, saying, ‘Beware that you do not go up on the mountain or touch the border of it; whoever touches the mountain shall surely be put to death.