Exodus 19:12-16

You shall set bounds for the people all around, saying, ‘Take heed to yourselves that you do not go up to the mountain or touch its base. Whoever touches the mountain shall surely be put to death. Not a hand shall touch him, but he shall surely be stoned or shot with an arrow; whether man or beast, he shall not live.’ When the trumpet sounds long, they shall come near the mountain.” So Moses went down from the mountain to the people and sanctified the people, and they washed their clothes. And he said to the people, “Be ready for the third day; do not come near your wives.” Then it came to pass on the third day, in the morning, that there were thunderings and lightnings, and a thick cloud on the mountain; and the sound of the trumpet was very loud, so that all the people who were in the camp trembled.