Shemot 19:9-11

Orthodox Jewish Bible

⁹ And Hashem said unto Moshe, Hinei, I am coming unto thee in a thick cloud, that HaAm may hear when I speak with thee, and believe thee l’olam. Then Moshe told the words of HaAm unto Hashem.

¹⁰ So Hashem said unto Moshe, Go unto HaAm, and set them apart as kodesh today and tomorrow, and let them wash their clothing,

¹¹ And be ready by Yom HaShelishi; for Yom HaShelishi Hashem will come down in the sight of kol HaAm upon Mt. Sinai.