Exodus 19:14-16

King James Version

¹⁴ And Moses went down from the mount unto the people, and sanctified the people; and they washed their clothes.

¹⁵ And he said unto the people, Be ready against the third day: come not at your wives.

¹⁶ And it came to pass on the third day in the morning, that there were thunders and lightnings, and a thick cloud upon the mount, and the voice of the trumpet exceeding loud; so that all the people that was in the camp trembled.