Any doubt that might nevertheless arise can be traced to one of three causes: either some mental impairment afflicted the parents, or a severe provocation compelled one of them to kill his child, or the killing has not been conclusively proven to have been a fully intentional act.

Likewise, excluded from the general ruling is the case in which a Muslim is not executed for killing a non-Muslim. This is established by the Sunnah, the verse addresses the believers alone, and it would not be just to put to death one of Allah’s allies for the sake of His enemy.

• “And the slave for the slave” (Qur’an 2:178)—whether male or female, whether their monetary value is equal or unequal. From this, it follows by implication that a free person is not to be executed for killing a slave, since the two are not juridically equal.

• The verse also shows that the original ruling in deliberate, hostile homicide is the obligation of retaliatory execution (qiṣāṣ), and that the diyah (blood-money) stands as its substitute. Hence Allah says, “But if any pardon is granted by his brother regarding anything…” (Qur’an 2:178), that is, the guardian of the victim waives retaliation in favor of diyah, or some of the heirs do so; in either case qiṣāṣ is waived and the diyah becomes mandatory.

• The discretion to choose between retaliation and accepting diyah rests with the guardian. If he pardons the killer, he must then pursue the payment courteously, without overburdening him or demanding what he cannot manage, but rather request it politely and without causing distress.

The killer, for his part, must pay it in an excellent manner—without delay, without diminution, and without any verbal or physical abuse. Is there any reward for the kindness shown to him through pardon other than repaying it with a gracious settlement?

This etiquette is required in every case where a right is owed:
• the creditor is instructed to pursue it in a decent manner;
• and the debtor is instructed to discharge it with excellence.