The Book Pertaining to the Oath, for Establishing the Responsibility of Murders, Fighting, Requital and Blood-Wit (Kitab Al-Kitab Al-Qasama wa'l-Muharaba wa'l-Qisas wa'l-Diyat)
Muslim :: Book 16 : Hadith 4158
'Abdullah b. (Mas'ud) reported Allah's Messenger (may peace be upon him) as saying: The first (thing) that will be decided among people on the Day of Judgment will pertain to bloodshed.