From Sahih Muslim (Hadith 7193):
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 (ﷺ) said:I saw 'Amr b. 'Amir al-Khuzili dragging his intestines in fire and he was the first who devoted animals to deity
Reference: Muslim 7193