Exodus 19:8

5 Now therefore, if you will indeed obey my voice, and keep my covenant, then you shall be my own possession from among all peoples; for all the earth is mine;

6 and you shall be to me a kingdom of priests, and a holy nation.` These are the words which you shall speak to the children of Israel."

7 Moses came and called for the elders of the people, and set before them all these words which Yahweh commanded him.

8 All the people answered together, and said, "All that Yahweh has spoken we will do." Moses reported the words of the people to Yahweh.

9 Yahweh said to Moses, "Behold, I come to you in a thick cloud, that the people may hear when I speak with you, and may also believe you forever." Moses told the words of the people to Yahweh.

10 Yahweh said to Moses, "Go to the people, and sanctify them today and tomorrow, and let them wash their garments,

11 and be ready against the third day; for on the third day Yahweh will come down in the sight of all the people on Mount Sinai.