Muwatta Malik: Setting Free and Wala’ — It was not permissible for a slave to buy himself from his master on the… (Hadith No. 1483)

Malik said that it was not permissible for a slave to buy himself from his master on the provision that he could give the wala' to whomever he wished as the wala' was for the one who set him free, and that had a man given permission to his mawla to give the wala' to whomever he wished, that would not have been permitted, because the Messenger of Allah, may Allah bless him and grant him peace, had said, "The wala' is for the one who sets free. " The Messenger of Allah, may Allah bless him and grant him peace, forbade selling or giving away the wala'. For if it was permitted to the master to stipulate that for him and to give him permission to give the wala' to whomever he liked, that would be a gift. Malik related to me from Rabia ibn Abd ar-Rahman that az-Zubayr ibn al-Awwam bought a slave and set him free. The slave had children by a free woman. When az-Zubayr freed him, he said, "They are my mawali." The man argued, "They are the mawali of their mother. Rather, they are our mawali." They took the dispute to Uthman ibn Affan, and Uthman gave a judgement that az-Zubayr had their wala

Explanation:

Reference: Muwatta Malik: Setting Free and Wala', Hadith No. 1483