Narrated Said bin Al-Musaiyab:
Bahira is a she-camel whose milk is kept for the idols and nobody is allowed to milk it;
Sa'iba was the she-camel which they used to set free for their gods and nothing was allowed to be carried on it. Abu Huraira said: Allah's Apostle ﷺ said, "I saw 'Amr bin 'Amir Al-Khuzai (in a dream) dragging his intestines in the Fire, and he was the first person to establish the tradition of setting free the animals (for the sake of their deities)," Wasila is the she-camel which gives birth to a she-camel as its first delivery, and then gives birth to another she-camel as its second delivery. People (in the Pre-lslamic periods of ignorance) used to let that she camel loose for their idols if it gave birth to two she-camels successively without giving birth to a male camel in between. 'Ham' was the male camel which was used for copulation. When it had finished the number of copulations assigned for it, they would let it loose for their idols and excuse it from burdens so that nothing would be carried on it, and they called it the 'Hami.' Abu Huraira said, "I heard the Prophet saying so."
Sahih al-Bukhari, Vol. 6, Book of Prophetic Commentary on the Qur'an, Hadith 147
Sahih al-Bukhari, Book of Prophetic Commentary on the Qur'an, Hadith 147