Exodus 19:12-19

ISV(i) 12 You are to set boundaries for the people all around: ‘Be very careful that you don’t go up on the mountain or touch the side of it. Anyone who touches the mountain is certainly to be put to death. 13 No hand is to touch that person, but he is certainly to be stoned or shot; whether animal or person, he is not to live.’ They are to approach the mountain only when the ram’s horn sounds a long blast.”
14 When Moses went down from the mountain to the people, he consecrated the people, and they washed their clothes. 15 He told the people, “Be ready for the third day; don’t go near a woman.”
16 The LORD Appears on Mount SinaiWhen morning came on the third day, there was thunder and lightning, with a heavy cloud over the mountain, and the very loud sound of a ram’s horn. All the people in the camp trembled. 17 Moses brought the people from the camp to meet God, and they stood at the base of the mountain. 18 Mount Sinai was completely enveloped in smoke because the LORD had come down in fire on it. Smoke went up from it like smoke from a kiln, and the whole mountain shook violently. 19 As the sound of the ram’s horn grew louder and louder, Moses would speak and God would answer with thunder.