She asked the Prophet of Allah ﷺ about a woman who experiences in her dream what a man experiences. The Messenger of Allah ﷺ replied, "If a woman sees that, she must perform a full bath."Umm Sulaym said, "I felt embarrassed by this." She then asked, "Does this really happen?"The Prophet of Allah ﷺ answered, "Yes. From where else would the resemblance come? The man's fluid is thick and white, while the woman's fluid is thin and yellow. Whichever of the two prevails or comes first, the resemblance will be from it."
أنها سألت نبي الله ﷺ عن المرأة ترى في منامها ما يرى الرجل، فقال رسول الله ﷺ: إذا رأت ذلك المرأة فلتغتسل. قالت أم سليم: واستحييت من ذلك. قالت: وهل يكون هذا؟ فقال نبي الله ﷺ: نعم، فمن أين يكون الشبه؟ إن ماء الرجل غليظ أبيض، وماء المرأة رقيق أصفر، فمن أيهما علا أو سبق يكون منه الشبه.
Muslim narrated it in the Book of Menstruation (311), from Abbas bin Walid, who said, Yazid bin Zuray narrated to us, Saeed narrated to us, from Qatada, that Anas bin Malik narrated to them from Umm Salim, and he mentioned it.