Sahih Muslim
The Book Pertaining to the Oath, for Establishing the Responsibility of Murders, Fighting, Requital and Blood-Wit (Kitab Al-Kitab Al-Qasama wal-Muharaba wal-Qisas wal-Diyat)
Book Number: 016 / Hadith Number: 4127
Sulaiman b. Yasar, the freed slave of Maimuna, the wife of Allah's Apostle (may peace be upon him), narrated from one of the Ansari Companions of Allah's Messenger (may peace be upon him) that Allah's Messenger (may peace be upon him) retained (the practice) of Qasama as it was in the pre-Islamic days.