Ibn Sirin (may Allah have mercy on him) says that Qadi Shurayh (may Allah have mercy on him) was asked about selling the children of a mukatabah, and he said: "The children are like her: if the mukatabah is freed, the children are also freed; if she is a slave, the children are also slaves."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المكاتب / 21700
Ibrahim (may Allah have mercy on him) says: The mukatabah may sell her child to be freed, using it to help with her kitabah. But the view of Qadi Shurayh (may Allah have mercy on him) was more preferable to Sufyan (may Allah have mercy on him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المكاتب / 21701
Ibn Jurayj (may Allah have mercy on him) said to Ata' (may Allah have mercy on him): "The mukatab does not stipulate that whatever children are born will be within my kitabah, and then children are born?" He said: "They are within his kitabah." Amr bin Dinar said the same.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المكاتب / 21702
Ibn Abi Mulaykah narrates that a slave woman was given a kitabah contract, then she gave birth to two children, then she died. I asked Abdullah bin al-Zubayr (may Allah be pleased with him) about her, and he said: "If the two of them take up their mother's kitabah, that is their right, and if they pay it off, they are freed."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المكاتب / 21703
Ata' bin Abi Rabah (may Allah have mercy on him) says: If he made a kitabah contract while he had no children, then children were born to him from a slave woman, and the father died, the price will not be reduced for them; they will remain on their father's kitabah, and if they wish, the kitabah may be cancelled and they remain slaves.
Hence we say: When a mukatab or a mukatabah dies without paying the amount, they remain slaves, and their children will also be slaves, with the evidence being the hadith: "If even one dirham remains due from him, he is still a slave."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المكاتب / 21704
Ibn Jurayj (may Allah have mercy on him) says: I said to Ata' (may Allah have mercy on him): "A man made a kitabah contract with his slave and settled with him, and the slave concealed from him property of his, slaves and other wealth." He said: "It belongs to his master."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المكاتب / 21705
Ibn Jurayj (may Allah have mercy on him) says: I said to Ata' (may Allah have mercy on him): "If the master asked the slave about his wealth and he concealed it?" He said: "It belongs to the master." Ibn Jurayj (may Allah have mercy on him) says: I asked Ata' (may Allah have mercy on him): "If he concealed a child of his from a slave woman, or he was not asked about it?" He said: "That too belongs to the master." Ibn Jurayj (may Allah have mercy on him) says: "If the master knew of the slave's child but it was not mentioned at the time of the kitabah?" He said: "That too is the master's property."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المكاتب / 21706