Shemot (Exodus): Yitro > Ch 19
Children of Israel encamp in the desert of Sinai opposite the mountains. G-d prepares Israel for His descent upon Mt. Sinai
They arrive in the 3rd month after departure from Egypt.
Moses ascended to G-d, and G-d told him:
So shall you say to the house of Jacob and tell the sons of Israel, You have seen what I did to the Egyptians, and [how] I bore you on eagles' wings, and I brought you to Me. And now, if you obey Me and keep My covenant, you shall be to Me a treasure out of all peoples, for Mine is the entire earth. And you shall be to Me a kingdom of princes and a holy nation.
Moses summoned the elders of Israel and all the people replied in unison and said, "All that the Lord has spoken we shall do!"
G-d told Moses:
Behold, I am coming to you in the thickness of the cloud, in order that the people hear when I speak to you, and they will also believe in you forever.
Go to the people and prepare them today and tomorrow, and they shall wash their garments. And they shall be prepared for the third day,
For on the third day, the Lord will descend before the eyes of all the people upon Mount Sinai.
And you shall set boundaries for the people around, saying, Beware of ascending the mountain or touching its edge; whoever touches the mountain shall surely be put to death.'
No hand shall touch it, for he shall be stoned or cast down; whether man or beast, he shall not live.
When the ram's horn sounds a long, drawn out blast, they may ascend the mountain."
Moses descended from the mountain and he prepared the people, and they washed their garments. He said to the people, "Be ready for three days; do not go near a woman."
G-d descends upon Mt. Sinai
On the third day, in the morning,
There were thunder claps and lightning flashes
And a thick cloud was upon the mountain
And a very powerful blast of a shofar
The entire nation that was in the camp shuddered. Moses brought the people out toward G-d from the camp, and they stood at the bottom of the mountain.
The entire Mount Sinai smoked because the Lord had descended upon it in fire, and its smoke ascended like the smoke of the kiln
And the entire mountain quaked violently.
The sound of the shofar grew increasingly stronger; Moses would speak and G-d would answer him with a voice. G-d descended to the peak of Mount Sinai, He summoned Moses and told him:
Go down, warn the people lest they break [their formation to go nearer] to the Lord, and many of them will fall. And also, the priests who go near to the Lord shall prepare themselves, lest the Lord wreak destruction upon them.
Moses replied that the people have already been warned, but G-d insisted that Moses should warn them again. Moses did so, then ascended again and brought Aaron with him as G-d has commanded.
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