Exodus 19:12-16

Put boundaries for the people all around the mountain and say: Be careful that you don’t go up on the mountain or touch its base. Anyone who touches the mountain must be put to death.  No hand may touch him;  instead he will be stoned or shot with arrows and not live, whether animal or human. When the ram’s horn sounds a long blast, they may go up the mountain.” Then Moses came down from the mountain to the people and consecrated them, and they washed their clothes. He said to the people, “Be prepared by the third day. Do not have sexual relations with women.” On the third day, when morning came, there was thunder and lightning, a thick cloud on the mountain, and a very loud blast from a ram’s horn, so that all the people in the camp shuddered.