Exodus 19:12-16

But you must set a limit around the mountain that the people are not to cross. Tell them not to go up on the mountain and not to touch the foot of it. Anyone who touches the mountain must be put to death with stones or shot with arrows. No one is allowed to touch him. Whether it is a person or an animal, he will not live. But the trumpet will make a long blast, and only then may the people go up on the mountain.” After Moses went down from the mountain to the people, he made them prepare themselves for service to God, and they washed their clothes. Then Moses said to the people, “Be ready in three days. Do not have sexual relations during this time.” On the morning of the third day, there was thunder and lightning with a thick cloud on the mountain. There was a very loud blast from a trumpet, and all the people in the camp trembled.