Yahya related to me from Malik from Ibn Shihab from Urwa ibn az-Zubayr that a mawla of the tribe of Banu Adi called Zabra told himthat she had been the wife of a slave when she was a slave-girl. Thenshe was set free and she sent a message to Hafsa, the wife of theProphet, may Allah bless him and grant him peace. Hafsa called her andsaid, "I will tell you something., but I would prefer that you did notact upon it. You have authority over yourself as long as your husbanddoes not have intercourse with you. If he has intercourse with you,you have no authority at all." Therefore she pronounced her divorcefrom him three times.
USC-MSA web (English) reference: Book 29, Hadith 27
Arabic reference: Book 29, Hadith 1184