And the term “legal retribution” denotes equivalence and equality, indicating that Allah has enjoined justice and fairness concerning those slain. Whoever kills anyone other than the killer of the person whose death he is avenging acts unjustly. Likewise, if the slain person and his heirs refuse to give the heirs of the other slain person their due, they are unjust. The former depart from the justice Allah has enjoined, and so do the latter.
He, glorified be He, expressed this meaning in His words:
“If anyone is killed unjustly, We have given his heir authority; but let him not exceed the limits in killing, for he is supported.”
Once the verse is understood to indicate justice in retaliation through necessary implication and implicit indication, the difficulty disappears. One will no longer ask: “Why, then, did He not say, ‘a slave for a slave and a free person’?” For the intended meaning was not that the one should be offset against the other among the slain. It is well known that, when claims are offset, a free man is matched with a free man, not a woman; a woman with a woman, not a free man; and a slave with a slave. Thus, the purpose of specifying these categories and matching them against one another in the verse becomes clear.
The verse then indicates that a free person is put to death for killing a free person, a slave for killing a slave, and a female for killing a female, provided the two are equal in respect of blood, the compensation for which is blood-money. This does not exclude putting a slave to death for killing a free person, or a female for killing a male; nor does the verse carry any implied meaning that excludes this. Rather, just as it indicates the former through implicit indication, the import of its wording, and a fortiori reasoning, it likewise indicates the latter. For if a slave is put to death for killing a slave, there is all the more reason to put him to death for killing a free person; and if a woman is put to death for killing a woman, there is all the more reason to put her to death for killing a man.