What is the legal status of offspring born to a slave woman whom the master permits his male slave (Mudabbar) to take as a concubine?

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The offspring follow the Mudabbar father in terms of the will for manumission (Tadbir). This view is narrated from Ahmad and Malik, and it is one of the two opinions in the Shafi'i school. The evidence for this is that the permissibility of concubinage (tasarri) is based on established ownership. Just as the child of a free man born to his slave follows the mother in freedom but not necessarily in freedom upon the master's death, similarly, the child of the Mudabbar follows the father in the right to manumission but not necessarily in the same status. Furthermore, since the child is born from a woman belonging to someone who is destined for freedom, the child follows him in that right, analogous to the child of a Mukatab (a slave contracted for his freedom) born to his slave woman.