Sahih Muslim | Book 40 | Hadith Number 6839
Narrated by Sa'id b. Musayyib
Sa'id b. Musayyib explained "al-bahira" as that animal which is not milked but for the idols and none amongst the people milks them, and "as-sa'iba" as that animal which is let loose for the deities. Nothing is loaded over it, and Ibn Musayyib narrated that Abu Huraira stated that Allah's Messenger (may peace be upon him) said: I saw 'Amr b. 'Amir al-Khuzili dragging his intestines in fire and he was the first who devoted animals to deity.