Sunan an-Nasai Book 45, Hadith 4781

قَالَ الْحَارِثُ بْنُ مِسْكِينٍ قِرَاءَةً عَلَيْهِ وَأَنَا أَسْمَعُ، عَنْ سُفْيَانَ، عَنْ عَمْرٍو، عَنْ مُجَاهِدٍ، عَنِ ابْنِ عَبَّاسٍ، قَالَ كَانَ فِي بَنِي إِسْرَائِيلَ الْقِصَاصُ وَلَمْ تَكُنْ فِيهِمُ الدِّيَةُ فَأَنْزَلَ اللَّهُ عَزَّ وَجَلَّ ‏{‏ كُتِبَ عَلَيْكُمُ الْقِصَاصُ فِي الْقَتْلَى الْحُرُّ بِالْحُرِّ وَالْعَبْدُ بِالْعَبْدِ وَالأُنْثَى بِالأُنْثَى ‏}‏ إِلَى قَوْلِهِ ‏{‏ فَمَنْ عُفِيَ لَهُ مِنْ أَخِيهِ شَىْءٌ فَاتِّبَاعٌ بِالْمَعْرُوفِ وَأَدَاءٌ إِلَيْهِ بِإِحْسَانٍ ‏}‏ فَالْعَفْوُ أَنْ يَقْبَلَ الدِّيَةَ فِي الْعَمْدِ وَاتِّبَاعٌ بِمَعْرُوفٍ يَقُولُ يَتَّبِعُ هَذَا بِالْمَعْرُوفِ وَأَدَاءٌ بِإِحْسَانٍ وَيُؤَدِّي هَذَا بِإِحْسَانٍ ‏{‏ ذَلِكَ تَخْفِيفٌ مِنْ رَبِّكُمْ وَرَحْمَةٌ ‏}‏ مِمَّا كُتِبَ عَلَى مَنْ كَانَ قَبْلَكُمْ إِنَّمَا هُوَ الْقِصَاصُ لَيْسَ الدِّيَةَ ‏.‏

It was narrated that Ibn 'Abbas said:"There was Qisas among the Children of Israel, but Diyah was unknown among them. Then Allah, the Mighty and Sublime, revealed: "Al-Qisas (the law of equality in punishment) is prescribed for your in case of murder: the free for the free, the slave for the slave, and the female for the female." Up to His saying: "But if the killer is forgiven by the brother 9or the relatives) of the killed against blood money, then adhering to it with fairness and payment of the blood money to the heir should be made in fairness."[2] Forgiveness means accepting the Diyah in the case of deliberate killing. Adhering to it in fairness means asking him to pay the Diyah in a fair manner, and payment in fairness means giving the Diyah in a fair manner. This is and alleviation and a mercy from you Lord,[1] means: This is easier thanthat which was prescribed for those who came before you, which was Qisas and not Diyah