Exodus 19:15 in the King James Version
And he said unto the people, Be ready against the third day: come not at your wives.
Context
14 Moses went down from the mountain to the people, and sanctified the people; and they washed their clothes.
15 He said to the people, “Be ready by the third day. Don’t have sexual relations with a woman.”
16 On the third day, when it was morning, there were thunders and lightnings, and a thick cloud on the mountain, and the sound of an exceedingly loud trumpet; and all the people who were in the camp trembled.