they accepted Islam. Our position is that this is an exchange that is not obligatory to accept, so it is not forbidden to kill them, just like the exchange for idolaters.
Section: When a slave is captured, he becomes a slave to the Muslims; because he is property belonging to them that has been seized, so he belongs to the victors, like livestock. If the Imam deems it appropriate to kill him due to the harm his presence causes, it is permissible to kill him; because someone like this has no value, and he is like an apostate. As for those whose killing is forbidden besides women and children, such as an elderly man, a chronically ill person, a blind person, and a monk, it is not permissible to enslave them; because killing them is forbidden, and there is no benefit in keeping them.
Section: Abu Bakr mentioned that if a disbeliever is the mawla (client/protege) of a Muslim, it is not permissible to enslave him; because in his enslavement, there is the nullification of the wala' (clientage right) of a protected Muslim. According to his view, his offspring are also not to be enslaved if they are under such clientage, for that same reason. If the one who emancipated him is a dhimmi (protected non-Muslim), it is permissible to enslave him; because it is permissible to enslave his master, so enslaving his client is more appropriate. This is the school of al-Shafi'i. The apparent meaning of the words of al-Khiraqi is the permissibility of enslaving him; because it is permissible to kill him, and he is one of the People of the Book, so it is permissible to enslave him, like others. Furthermore, the reason for the permissibility of enslavement has been realized in his case, which is the seizing of him, along with the fact that the interest of the Muslims lies in his enslavement. Also, if the captive were a woman or a child, nothing would be permissible regarding them except enslavement, so it becomes the determined course for them. What he (Abu Bakr) mentioned is invalidated by the fact of killing; for it nullifies the wala', yet it is permissible in his case. Likewise, one who is under the clientage of a dhimmi may be enslaved. Their statement that "his master may be enslaved" is incorrect; for it is not permissible to enslave a dhimmi, nor to nullify his rights. Ali, may Allah be pleased with him, said: "They only offered the jizya so that their blood would be like our blood, and their wealth like our wealth" (20).
1635 - Issue: He said: (The course for those of them who are enslaved, and what is taken from them upon their release, is the course of that booty).
He means whoever among them becomes a slave by the application of the status of slavery upon him, or is ransomed for wealth, he is like the rest of the booty. It is divided into fifths, then four-fifths of it is distributed among the victors. We know of no disagreement regarding this; for the Prophet (peace and blessings of Allah be upon him)
(20) See: Nasb al-Rayah 3/381.