Yahya related to me from Malik from Hisham ibn Urwa from his
father from Zaynab bint Abi Salama that Umm Salama, the wife of the
Prophet, may Allah bless him and grant him peace, said, "Umm Salama,
the wife of Abu Talha al-Ansari, came to the Messenger of Allah, may
Allah bless him and grant him peace, and said, 'Messenger of Allah!
Allah is not ashamed of the truth-does a woman have to do ghusl if she
has had an erotic dream?' He said, 'Yes, if she sees any liquid.' "
Muwatta Malik Book 2, Hadith 86