Al-Muwatta Hadith 39.8

Malik related to me that he heard that Urwa ibn az-Zubayr and Sulayman ibn Yasar when asked whether the sons of a man, who had a kitaba written for himself and his children and then died, worked for the kitaba of their father or were slaves, said, "They work for the kitaba of their father and they have no reduction at all for the death of their father." Malik said, "If they are small and unable to work, one does not wait for them to grow up and they are slaves of their father's master unless the mukatab has left what will pay their instalments for them until they can work. If there is enough to pay for them in what he has left, that is paid for on their behalf and they are left in their condition until they can work, and then if they pay, they are free. If they cannot do it, they are slaves." Malik spoke about a mukatab who died and left property which was not enough to pay his kitaba, and he also left a child with him in his kitaba and an umm walad, and the umm walad wanted to work for them. He said, "The money is paid to her if she is trustworthy with it and strong enough to work. If she is not strong enough to work and not trustworthy with property, she is not given any of it and she and the children of the mukatab revert to being slaves of the master of the mukatab." Malik said, "If people are written together in one kitaba and there is no kinship between them, and some of them are incapable and others work until they are all set free, those who worked can claim from those who were unable, the portion of what they paid for them because some of them assumed the responsibility for others."