Exodus 19:10 in the King James Version
And the LORD said unto Moses, Go unto the people, and sanctify them to day and to morrow, and let them wash their clothes,
Context
9 The LORD 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 the LORD.
10 The LORD said to Moses, “Go to the people, and sanctify them today and tomorrow, and let them wash their garments,
11 and be ready for the third day; for on the third day the LORD will come down in the sight of all the people on Mount Sinai.