Exodus 19:11-15

19:11 and 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. 19:12 You must set boundaries for the people all around, saying, ‘Take heed to yourselves not to go up on the mountain nor touch its edge. Whoever touches the mountain will surely be put to death! 19:13 No hand will touch him – but he will surely be stoned or shot through, whether a beast or a human being; he must not live.’ When the ram’s horn sounds a long blast they may go up on the mountain.”

19:14 Then Moses went down from the mountain to the people and sanctified the people, and they washed their clothes. 19:15 He said to the people, “Be ready for the third day. Do not go near your wives.”