O believers, ordained for you is retribution for the murdered, (whether) a free man (is guilty) of (the murder of) a free man, or a slave of a slave, or a woman of a woman. But he who is pardoned some of it by his brother should be dealt with equity, and recompense (for blood) paid with a grace. This is a concession from your Lord and a kindness. He who transgresses in spite of it shall suffer painful punishment.
— Quran 2:178