The people of Islam do not set animals free as sawaib, but the people of the pre-Islamic era used to do so.
إن أهل الإسلام لا يسيبون، وإن أهل الجاهلية كانوا يسيبون.
Bukhari reported it in the Book of Inheritance (6753) from Qabisa bin Uqba, who said, Sufyan narrated to us, from Abu Qays, from Hazeel, from Abdullah, and he mentioned it as a mawquf report (stopped at the Companion).As for his statement, "saibah," it means that a master says to his slave, "No one has any wala over you," or "You are saibah," meaning by that his emancipation and that no one has wala over him. He might also say to him, "I free you as saibah," or "You are free, as saibah."The hadith of Abdullah bin Masud here is only a portion of a hadith that Ismaili reported in full, through the route of Abdul-Rahman bin Mahdi, from Sufyan, with his chain reaching Hazeel, who said, a man came to Abdullah and said, "I freed a slave of mine as saibah, and he died, leaving property but no heir." Abdullah then said what is mentioned in this chapter's hadith, and added, "You are the one who granted him his blessing (of freedom), so his inheritance is yours. But if you feel it would be sinful or improper to take any of it, we will accept it and place it in the treasury." This is as found in Fath al-Bari (12/41).Abdul-Razzaq (16223) likewise reported it from Thawri with his chain, similarly. Abdul-Razzaq (16222) also reported from Mamar, from Qatada, that a man came to Ibn Masud and said, "A freedman of mine has died. I had freed him as saibah, and he left property." Ibn Masud said, "You have more right to his property." The man said, "But I only freed him for Allah's sake." Ibn Masud said, "You have more right to his property. If you leave it, then you will find that it has many heirs here," meaning the treasury.Abdul-Razzaq (16232) also reported from Mamar, from Ayub, from Ibn Sirin, that Salim, the freedman of Abu Huzaifa, had been freed by a woman from the Ansar. When he was killed on the day of Yamama, his inheritance was given to the Ansari woman who had freed him, or to her son.From Ibn Ishaq, who said, Abdullah bin Abu Bakr bin Muhammad bin Amr bin Hazm narrated to me, from Abdullah bin Wadia bin Khidam bin Khalid, brother of Banu Amr bin Awf, who said, Salim, the freedman of Abu Huzaifa, had been the freedman of a woman among us called Salma bint Yaar, who had freed him as saibah in the pre-Islamic period. When he was killed at Yamama, his inheritance was brought to Umar bin Khattab, who summoned Wadia bin Khidam and said, "This is the inheritance of your freedman, and you have more right to it." Wadia said, "O Commander of the Faithful, Allah has made us independent of it. Our woman freed him as saibah, and we do not wish to attach ourselves to any part of his affair," or he said, "to burden ourselves with it." So Umar placed it in the treasury.Yaqub bin Sufyan reported it in Al-Marifa, and through his route Bayhaqi (10/300) reported, Muhammad bin Mansur narrated to us, Yaqub bin Ibrahim bin Saad narrated to us, my father informed us, from Ibn Ishaq, who mentioned it. Its chain is hasan because of Muhammad bin Ishaq, for although he is a mudallis, he has here stated clearly that he heard it directly.On this subject there are other reports mentioned by Abdul-Razzaq, Bayhaqi, and others.As for the sayings of the scholars concerning the saibah, among them is the view of Shafii, that the emancipation stands, and the wala belongs to the one who freed him, but if he is reluctant to take it, then it is placed in the treasury. Among them is the view that the inheritance of the saibah belongs to the Muslims, who inherit it and bear the blood money obligation for him, and this is the view held by Malik. Among them is the view that there is no harm in selling or gifting the wala of the saibah, and this is the view held by the Kufans, and it is also the view of Ibrahim and Shaybi.What Shafii held is what is apparent from the texts, and from the statement of the Prophet ﷺ, "Wala belongs to the one who frees." This is also the view held by Bukhari, for after the report of Ibn Masud, he brought the hadith of Ayesha, in which he said to her, "Free her, for wala belongs to the one who frees."