The valid one, for it established ownership of the object of exchange, thus it established it in the object being exchanged. The fourth is: Does her offspring follow the mukataba? Abu al-Khattab said: There are two views regarding this; one of them is that he follows her, because it is a kitaba in which she becomes free upon fulfillment, so her offspring becomes free by it, like the valid kitaba. The second is that he does not follow her, and this is more analogous and more correct, due to what we mentioned regarding the one before it, and because the original state is the continuation of servitude for him, so it does not cease except by a text, or the meaning of a text, and neither one of them is found. Analogy to the valid kitaba is not correct, due to the difference we mentioned between them previously, so it remains upon the original state. And Allah knows best.

Book of the Emancipation of Umm al-Walad (Mothers of Children)

The umm al-walad: She is the one who has given birth from her master while in his possession. There is no disagreement regarding the permissibility of concubinage and having sexual relations with slave women; according to the saying of Allah the Almighty: {And those who guard their private parts, except from their spouses or those their right hands possess, for then they are not to be blamed}. Maria the Copt was an umm al-walad to the Prophet (peace and blessings of Allah be upon him), and she is the mother of Ibrahim, the son of the Prophet (peace and blessings of Allah be upon him), regarding whom he said: "Her offspring has emancipated her." Hajar, the mother of Ismail, peace be upon him, was a concubine to Ibrahim, the Khalil (Intimate Friend) of the Most Merciful, peace be upon him. Umar ibn al-Khattab, may Allah be pleased with him, had ummahat awlad for each of whom he bequeathed four hundred [dirhams]. Ali, may Allah be pleased with him, had ummahat awlad, as did many of the Companions. Ali ibn al-Husayn, al-Qasim ibn Muhammad, and Salim ibn Abd Allah were from ummahat awlad. It is narrated that people were not inclined toward ummahat awlad until these three were born from ummahat awlad, after which people became inclined toward them. It was narrated from Salim ibn Abd Allah that he said: Ibn Rawahah had a slave girl, and he wanted to be alone with her, and his wife was watching him. When the house became empty, he had intercourse with her, and his wife became aware of it.