Sahih Bukhari Volume 9, Book 87, Hadith 6883

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا سُفْيَانُ، عَنْ عَمْرٍو، عَنْ مُجَاهِدٍ، عَنِ ابْنِ عَبَّاسٍ ـ رضى الله عنهما ـ قَالَ كَانَتْ فِي بَنِي إِسْرَائِيلَ قِصَاصٌ، وَلَمْ تَكُنْ فِيهِمُ الدِّيَةُ فَقَالَ اللَّهُ لِهَذِهِ الأُمَّةِ ‏{‏كُتِبَ عَلَيْكُمُ الْقِصَاصُ فِي الْقَتْلَى‏}‏ إِلَى هَذِهِ الآيَةِ ‏{‏فَمَنْ عُفِيَ لَهُ مِنْ أَخِيهِ شَىْءٌ‏}‏‏.‏ قَالَ ابْنُ عَبَّاسٍ فَالْعَفْوُ أَنْ يَقْبَلَ الدِّيَةَ فِي الْعَمْدِ، قَالَ ‏{‏فَاتِّبَاعٌ بِالْمَعْرُوفِ‏}‏ أَنْ يَطْلُبَ بِمَعْرُوفٍ وَيُؤَدِّيَ بِإِحْسَانٍ‏.‏

Narrated By Ibn 'Abbas : For the children of Israel the punishment for crime was Al-Qisas only (i.e., the law of equality in punishment) and the payment of Blood money was not permitted as an alternate. But Allah said to this nation (Muslims): 'O you who believe! Qisas is prescribed for you in case of murder... (up to)... end of the Verse. (2.178) Ibn 'Abbas added: Remission (forgiveness) in this Verse, means to accept the Blood-money in an intentional murder. Ibn 'Abbas added: The Verse: 'Then the relatives should demand Blood-money in a reasonable manner.' (2.178) means that the demand should be reasonable and it is to be compensated with handsome gratitude.