Exodus 19:9-11

New Catholic Bible

⁹ The Lord said to Moses, “Behold, I am about to approach you in a thick cloud so that the people will hear when I speak to you and always believe in you.”

¹⁰ The Lord said to Moses, “Go to the people and consecrate them today and tomorrow. Have them wash their clothes ¹¹ and have them ready for the third day, for on the third day the Lord will come down upon Mount Sinai to visit all the people.