What is the ruling on retribution (qisas)?

The ruling on retribution (qisas) for the victim's guardians is permissibility, because they have the choice between retribution, pardon, or receiving blood money (diyya). One must adhere to the limit and not transgress it. Al-Tabari mentioned in his exegesis of the Almighty's saying: "O you who have believed, prescribed for you is legal retribution for those murdered — the free for the free, the slave for the slave, and the female for the female. But whoever is pardoned by his brother for something, then [the pursuit of payment should be] a gracious pursuit and payment to him with good conduct," that the meaning of "prescribed for you" (كتب عليكم) is "made obligatory upon you" (فرض عليكم). This does not mean that retribution is imposed upon the victim's guardian, but rather it is permissible for him, and he also has the option to pardon and take blood money. He interprets the verse to mean that retribution is prescribed in cases of murder, such that the free is an equal to the free, the slave an equal to the slave, and the female an equal to the female. Thus, it is not permissible to extend the killing to someone other than the killer.