Exodus 19:15

And he said unto the people, Be ready against the third day: come not at your wives.
— Exodus 19:15, King James Version

In other translations

World English Bible (WEB)

He said to the people, "Be ready by the third day. Don't have sexual relations with a woman."

American Standard Version (ASV)

And he said unto the people, Be ready against the third day: come not near a woman.

Young's Literal Translation (YLT)

and he saith unto the people, 'Be ye prepared for the third day, come not nigh unto a woman.'