Musnad Abu Ya'la al-Mawsili 209:126

Abu Khaythama narrated to us, Waki' narrated to us, Hisham narrated to us, from his father, from Zaynab bint Umm Salama, from Umm Salama, who said: Umm Sulaym came to the Prophet, may Allah bless him and grant him peace, and asked him about a woman who sees in her sleep what a man sees. He said: "If she sees the fluid, then she must perform ghusl (ritual bath)." I said: "You have disgraced the women! Does a woman have wet dreams?" The Prophet, may Allah bless him and grant him peace, said: "May your right hand be covered in dust! Then in what does her child resemble her?"