Exodus 19:1-12 KJV
In the third month, when the children of Israel were gone forth out of the land of Egypt, the same day came they into the wilderness of Sinai. For they were departed from Rephidim, and were come to the desert of Sinai, and had pitched in the wilderness; and there Israel camped before the mount. And Moses went up unto God, and the LORD called unto him out of the mountain, saying, Thus shalt thou say to the house of Jacob, and tell the children of Israel; ye have seen what I did unto the Egyptians, and how I bare you on eagles' wings, and brought you unto myself. Now therefore, if ye will obey my voice indeed, and keep my covenant, then ye shall be a peculiar treasure unto me above all people: for all the earth is mine: and ye shall be unto me a kingdom of priests, and an holy nation. These are the words which thou shalt speak unto the children of Israel.
And Moses came and called for the elders of the people, and laid before their faces all these words which the LORD commanded him. And all the people answered together, and said, All that the LORD hath spoken we will do. And Moses returned the words of the people unto the LORD. And the LORD said unto Moses, Lo, I come unto thee in a thick cloud, that the people may hear when I speak with thee, and believe thee for ever. And Moses told the words of the people unto the LORD.
And the LORD said unto Moses, Go unto the people, and sanctify them to day and to morrow, and let them wash their clothes, and be ready against the third day: for the third day the LORD will come down in the sight of all the people upon mount Sinai. And thou shalt set bounds unto the people round about, saying, Take heed to yourselves, that ye go not up into the mount, or touch the border of it: whosoever toucheth the mount shall be surely put to death