Exodus 19:10-15

10And the Lord said to Moses, “Go to the people and consecrate them today and tomorrow. Have them wash their clothes 11and be ready by the third day, because on that day the Lord will come down on Mount Sinai in the sight of all the people. 12Put limits for the people around the mountain and tell them, ‘Be careful that you do not approach the mountain or touch the foot of it. Whoever touches the mountain is to be put to death. 13They are to be stoned or shot with arrows; not a hand is to be laid on them. No person or animal shall be permitted to live.’ Only when the ram’s horn sounds a long blast may they approach the mountain.” 14After Moses had gone down the mountain to the people, he consecrated them, and they washed their clothes. 15Then he said to the people, “Prepare yourselves for the third day. Abstain from sexual relations.”