Exodus 19:16-25

So it happened on the third day, when it was morning, that there were thunder and flashes of lightning, and a thick cloud was on the mountain, and a very loud blast was sounded on a ram’s horn, so that all the people who were in the camp trembled. Then Moses brought the people out of the camp to meet God, and they stood and presented themselves at the foot of the mountain. ORD Mount Sinai was wrapped in smoke because the LORD descended upon it in fire; its smoke ascended like the smoke of a furnace, and the whole mountain quaked violently. And it happened, as the blast of the ram’s horn grew louder and louder, Moses spoke and God answered him with [a voice of] thunder. [Deut 4:12] The LORD came down on Mount Sinai, to the top of the mountain; and the LORD called Moses to the top of the mountain, and he went up. Then the LORD spoke to Moses, “Go down, warn the people, so that they do not break through [the barriers around the mountain] to the LORD to see [Me], and many of them perish [as a result]. Also have the priests who approach the LORD consecrate (sanctify, set apart) themselves [for My sacred purpose], or else the LORD will break forth [in judgment] against them [and destroy them].” Moses said to the LORD, “The people cannot come up to Mount Sinai, because You warned us, saying, ‘Set barriers around the mountain and consecrate it.’ ” Then the LORD said to him, “Go down and come up again, you and Aaron with you; but do not let the priests and the people break through [the barriers] to come up to the LORD, or He will break forth [in judgment] against them [and destroy them].” So Moses went down to the people and told them [again about God’s warning].