וְאִשָּׁ֕ה אֲשֶׁ֨ר יִשְׁכַּ֥ב אִ֛ישׁ אֹתָ֖הּ שִׁכְבַת־זָ֑רַע וְרָחֲצ֣וּ בַמַּ֔יִם וְטָמְא֖וּ עַד־הָעָֽרֶב׃
The woman also with whom a man shall lie carnally, they shall both bathe themselves in water, and be unclean until the even.
Read kabbalistic (mystical) interpretation of Leviticus 15:18: and classical mystical sources.