من لا يحضره الفقيه, volume 3, page 122

Hadith.3463 - Asim narrated from Abu Basir, who said: I asked him about a male or female slave who had been made mudabbar (to be freed after the master's death). Imam (as) said: "The master may enter into a mukataba (a contract of emancipation in exchange for payment) with the slave if he wishes. However, he cannot sell the slave unless the slave agrees to be sold for the duration of the master's life. The master is also entitled to take any wealth the slave possesses, if the slave has wealth."

Translation: Bab Ul Qaim Publications·Thaqalayn link·The Arabic above is the original.

Hadith.3464 - Abdullah ibn Sinan asked him about a woman who freed one-third of her servant at the time of her death. He asked: "Are her heirs required to enter into a mukataba (a contract of emancipation in exchange for payment) with the servant if they wish, or can they refuse?" Imam (as) said: "No, but the servant owns one-third of herself, and the heirs own two-thirds. The heirs may use her services in proportion to their share, and she has freedom over herself in proportion to the part that was freed."

Translation: Bab Ul Qaim Publications·Thaqalayn link·The Arabic above is the original.

Hadith.3465 - Aban narrated from Abd al-Rahman, who said: I asked him about a man who said to his slave, "If something happens to me, you are free." Meanwhile, the man is obligated to free a slave as an expiation for breaking an oath or zihar (a form of prohibited declaration regarding one's wife). I asked: "Can he use this same slave, whom he had promised freedom upon his death, to fulfill the requirement of freeing a slave for the expiation?" Imam (as) said: "No, it is not permissible to use the slave designated for that purpose."

Translation: Bab Ul Qaim Publications·Thaqalayn link·The Arabic above is the original.