Sayyiduna Ibn Abbas (may Allah be pleased with them both), regarding the saying of Allah Almighty: "Then (the matter) should be pursued with fairness and payment made to him with excellence" [Al-Baqarah: 178], said: "Among the Children of Israel, when someone was killed deliberately, nothing but retaliation (qisas) was lawful for them, and the concession of blood money (diyah) has been made lawful for you. So this one (the heir of the slain) was commanded to pursue it with fairness, and this one (the killer) was commanded to pay with excellence. That is an alleviation from your Lord [Al-Baqarah: 178]."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11109