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.”

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.