The Israelites arrived in the wilderness of Sinai exactly two months after they left Egypt.
References for Exodus 19:1
After breaking camp at Rephidim, they came to the base of Mount Sinai and set up camp there.
Then Moses climbed the mountain to appear before God. The LORD called out to him from the mountain and said, "Give these instructions to the descendants of Jacob, the people of Israel:
'You have seen what I did to the Egyptians. You know how I brought you to myself and carried you on eagle's wings.
Now if you will obey me and keep my covenant, you will be my own special treasure from among all the nations of the earth; for all the earth belongs to me.
And you will be to me a kingdom of priests, my holy nation.' Give this message to the Israelites."
Moses returned from the mountain and called together the leaders of the people and told them what the LORD had said.
They all responded together, "We will certainly do everything the LORD asks of us." So Moses brought the people's answer back to the LORD.
Then the LORD said to Moses, "I am going to come to you in a thick cloud so the people themselves can hear me as I speak to you. Then they will always have confidence in you." Moses told the LORD what the people had said.
Then the LORD told Moses, "Go down and prepare the people for my visit. Purify them today and tomorrow, and have them wash their clothing.
Be sure they are ready on the third day, for I will come down upon Mount Sinai as all the people watch.
Set boundary lines that the people may not pass. Warn them, 'Be careful! Do not go up on the mountain or even touch its boundaries. Those who do will certainly die!
Any people or animals that cross the boundary must be stoned to death or shot with arrows. They must not be touched by human hands.' The people must stay away from the mountain until they hear one long blast from the ram's horn. Then they must gather at the foot of the mountain."
So Moses went down to the people. He purified them for worship and had them wash their clothing.
He told them, "Get ready for an important event two days from now. And until then, abstain from having sexual intercourse."
On the morning of the third day, there was a powerful thunder and lightning storm, and a dense cloud came down upon the mountain. There was a long, loud blast from a ram's horn, and all the people trembled.
Moses led them out from the camp to meet with God, and they stood at the foot of the mountain.
All Mount Sinai was covered with smoke because the LORD had descended on it in the form of fire. The smoke billowed into the sky like smoke from a furnace, and the whole mountain shook with a violent earthquake.
As the horn blast grew louder and louder, Moses spoke, and God thundered his reply for all to hear.
The LORD came down on the top of Mount Sinai and called Moses to the top of the mountain. So Moses climbed the mountain.
Then the LORD told Moses, "Go back down and warn the people not to cross the boundaries. They must not come up here to see the LORD, for those who do will die.
Even the priests who regularly come near to the LORD must purify themselves, or I will destroy them."
"But LORD, the people cannot come up on the mountain!" Moses protested. "You already told them not to. You told me to set boundaries around the mountain and to declare it off limits."
But the LORD said, "Go down anyway and bring Aaron back with you. In the meantime, do not let the priests or the people cross the boundaries to come up here. If they do, I will punish them."
So Moses went down to the people and told them what the LORD had said.