Exodus 19:16-20

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. Then Moses brought the people out of the camp to meet God, and they stood at the foot of the mountain. Mount Sinai was completely enveloped in smoke because the LORD came down on it in fire. Its smoke went up like the smoke of a furnace, and the whole mountain shook violently. As the sound of the ram’s horn grew louder and louder, Moses spoke and God answered him in the thunder. The LORD came down on Mount Sinai at the top of the mountain. Then the LORD summoned Moses to the top of the mountain, and he went up.