ExodusChapter 19

In the third month after the Israelites left the land of Egypt, on that very day, they came to the wilderness of Sinai.
They set out from Rephidim, entered the wilderness of Sinai, and camped in the wilderness; there Israel camped in front of the mountain.
Then Moses went up to God, and the LORD called to him from the mountain: "This is what you are to say to the house of Jacob and tell the Israelites:
'You have seen for yourselves what I did to Egypt, and how I carried you on eagles' wings and brought you to myself.
Now then, if you will listen closely to my voice and keep my covenant, you will be my treasured possession out of all the peoples—for the whole earth is mine—
and you will be for me a kingdom of priests and a holy nation.' These are the words you are to speak to the Israelites."
So Moses went and summoned the elders of the people and set before them all these words that the LORD had commanded him.
And all the people answered together, "Everything the LORD has spoken, we will do." And Moses brought the people's words back to the LORD.
The LORD said to Moses, "Look, I am coming to you in a dense cloud, so that the people may hear when I speak with you and may always put their trust in you as well." Then Moses told the LORD what the people had said.
The LORD said to Moses, "Go to the people and consecrate them today and tomorrow. Have them wash their garments,
and be ready for the third day, because on the third day the LORD will come down on Mount Sinai in the sight of all the people.
Set limits for the people all around, and say: 'Be careful not to go up the mountain or touch its edge. Whoever touches the mountain must surely be put to death.
No hand shall touch him; he must be stoned or shot with arrows. Whether animal or human, he shall not live.' Only when the ram's horn sounds a long blast may they go up the mountain."
Moses came down from the mountain to the people, consecrated them, and they washed their garments.
He said to the people, "Be ready in three days; do not go near a woman."
On the morning of the third day there was thunder and lightning, a thick cloud over the mountain, and a very loud blast of a horn. Everyone in the camp trembled.
Then Moses led the people out of the camp to meet God, and they took their stand at the foot of the mountain.
Mount Sinai was completely wrapped in smoke, because the LORD had come down on it in fire. Its smoke rose like the smoke of a furnace, and the whole mountain shook violently.
As the sound of the horn grew louder and louder, Moses spoke, and God answered him with a voice.
The LORD came down on Mount Sinai, to the top of the mountain, and called Moses up to the top. So Moses went up.
The LORD said to Moses, "Go down and warn the people not to break through to the LORD to look, or many of them will perish.
Even the priests who come near the LORD must consecrate themselves, or the LORD will break out against them."
Moses said to the LORD, "The people cannot come up Mount Sinai, for you yourself warned us, saying, 'Set limits around the mountain and consecrate it.'"
The LORD said to him, "Go down, and come up again, you and Aaron with you. But the priests and the people must not break through to come up to the LORD, or he will break out against them."