[The third proof that it is forbidden to kill a disbeliever merely on account of his unbelief]
Moreover, Allah the Exalted says concerning the fighting of the unbelievers: “So when you meet those who disbelieve, strike their necks until, when you have devastated them, bind them firmly; then, thereafter, either show favor or demand ransom” (Q 47:4).
Had simple disbelief itself made execution obligatory, it would not have been permissible to grant an unbeliever his freedom or to ransom him, just as no clemency is allowed toward those whose execution is mandatory, such as the married adulterer or the apostate. Yet the Prophet ﷺ did in fact bestow clemency upon more than one unbeliever and ransomed many of them—for instance, he ransomed the captives taken at Badr (1).
If, however, they repent only after falling under the Muslims’ power, the entire prescribed punishment (*hudud*) is not waived, for doing so would disable the penal code and lead to corruption. Such repentance is not deemed trustworthy. Thus, when a *harbi* (enemy combatant) embraces Islam during the fighting, his conversion is valid because it occurs before the Muslims gain control over him; by contrast, if he accepts Islam after being taken captive, this does not preclude his enslavement, even though his life is now inviolable.
(1) Shaykh al-Islam Ibn Taymiyya states in his *Fatawa* (28:414): “An original non-Muslim may be granted *aman* (safe-conduct) or a truce; if captured, the majority allow either unconditional release or ransom. If he is from the People of the Book, a *dhimma* pact may be concluded with him; their food is lawful to eat, and their women may be lawfully married. Their women are not to be killed unless they participate in the fighting, whether by word or deed—this is agreed upon by the scholars. Likewise, none of them is to be put to death except one who …”