Аль-Бакара 2:178

O you who believe, prescribed, made obligatory, for you is retaliation, on equal terms, regarding the slain, both in the attributes [of the one slain] and in the action involved; a free man, is killed, for a free man, and not for a slave; and a slave for a slave, and a female for a female. The Sunna makes it clear that a male may be killed [in retaliation] for a female, and that religious affiliation should be taken into account also, so that a Muslim cannot be killed in return for an disbeliever, even if the former be a slave and the latter a free man. But if anything, of the blood, is pardoned any one, of those who have slain, in relation to his brother, the one slain, so that the retaliation is waived (the use of the indefinite shay’un, ‘anything’, here implies the waiving of retaliation through a partial pardon by the inheritors [of the slain]; the mention of akhīh [‘his brother’] is intended as a conciliatory entreaty to pardon and a declaration that killing should not sever the bonds of religious brotherhood; the particle man, ‘any one’, is the subject of a conditional or a relative clause, of which the predicate is [the following, fa’ittibā‘un]) let the pursuing, that is, the action of the one who has pardoned in pursuing the killer, be honourable, demanding the blood money without force. The fact that the ‘pursuing’ results from the ‘pardoning’ implies that one of the two [actions] is a duty, which is one of al-Shāfi‘ī’s two opinions here. The other [opinion] is that retaliation is the duty, whereas the blood money is merely compensation [for non-retaliation], so that if one were to pardon but not name his blood money, then nothing [happens]; and this [latter] is the preferred [opinion]. And let the payment, of the blood money by the slayer, to him, the pardoner, that is, the one inheriting [from the slain], be with kindliness, without procrastination or fraud; that, stipulation mentioned here about the possibility of retaliation and the forgoing of this in return for blood money, is an alleviation, a facilitation, given, to you, by your Lord, and a mercy, for you, for He has given you latitude in this matter and has not categorically demanded that one [of the said options] be followed through, in the way that He made it obligatory for Jews to retaliate and for Christians to [pardon and] accept blood money; and for him who commits aggression, by being unjust towards the killer and slaying him, after that, that is, [after] pardoning — his is a painful chastisement, of the Fire in the Hereafter, or of being killed in this world.