Is Mariya al-Qibtiyya considered one of the Mothers of the Believers, and if not, is it permissible for her to marry or be taken as a captive after the death of the Messenger of Allah, peace and blessings be upon him?

The Mothers of the Believers are the wives of the Prophet, peace and blessings be upon him, with whom he formally contracted marriage. Maria al-Qibtiyya was not among them because he did not contract marriage with her. Rather, she was a concubine to him and bore him Ibrahim. Although she is not among the Mothers of the Believers, it was not permissible for her to marry after his death, peace and blessings be upon him. Similarly, it is forbidden for anyone else to marry any woman with whom the Prophet, peace and blessings be upon him, had intimacy, whether she was a free woman or a slave. Scholars have agreed that Maria was a slave-concubine (umm walad) to the Prophet, peace and blessings be upon him, and that she was not sold after his death but became free.