וְכָל־בֶּ֣גֶד וְכָל־ע֔וֹר אֲשֶׁר־יִהְיֶ֥ה עָלָ֖יו שִׁכְבַת־זָ֑רַע וְכֻבַּ֥ס בַּמַּ֖יִם וְטָמֵ֥א עַד־הָעָֽרֶב׃ (פ)
And every garment, and every skin, whereon is the flow of seed, shall be washed with water, and be unclean until the even.
Read kabbalistic (mystical) interpretation of Leviticus 15:17: and classical mystical sources.