Exodus 19:13-16

No hand may touch the person or animal that crosses the boundary; instead, stone them or shoot them with arrows. They must be put to death.’ However, when the ram’s horn sounds a long blast, then the people may go up on the mountain.” So Moses went down to the people. He consecrated them for worship, and they washed their clothes. He told them, “Get ready for the third day, and until then abstain from having sexual intercourse.” On the morning of the third day, thunder roared and lightning flashed, and a dense cloud came down on the mountain. There was a long, loud blast from a ram’s horn, and all the people trembled.