וַיֹּ֙אמֶר֙ אֶל־הָעָ֔ם הֱי֥וּ נְכֹנִ֖ים לִשְׁלֹ֣שֶׁת יָמִ֑ים אַֽל־תִּגְּשׁ֖וּ אֶל־אִשָּֽׁה׃
And he said unto the people: ‘Be ready against the third day; come not near a woman.’
Read Kabbalistic (mystical) interpretations of Exodus 19:15: Zohar and classical Jewish mystical sources, free online.