The law of Qisas (i.e. equality in punishment) was prescribed for the children of Israel, but the Diya (i.e. blood money was not ordained for them). So Allah said to this Nation (i.e. Muslims): "O you who believe! The law of Al-Qisas (i.e. equality in punishment) is prescribed for you in cases of murder: The free for the free, the slave for the slave, and the female for the female. But if the relatives (or one of them) of the killed (person) forgive their brother (i.e. the killers something of Qisas (i.e. not to kill the killer by accepting blood money in the case of intentional murder)----then the relatives (of the killed person) should demand blood-money in a reasonable manner and the killer must pay with handsome gratitude. This is an allevitation and a Mercy from your Lord, (in comparison to what was prescribed for the nations before you). So after this, whoever transgresses the limits (i.e. to kill the killer after taking the blood-money) shall have a painful torment." (2.178)  

اللَّهُ تَعَالَى لِهَذِهِ الأُمَّةِ {كُتِبَ عَلَيْكُمُ الْقِصَاصُ فِي الْقَتْلَى الْحُرُّ بِالْحُرِّ وَالْعَبْدُ بِالْعَبْدِ وَالأُنْثَى بِالأُنْثَى فَمَنْ عُفِيَ لَهُ مِنْ أَخِيهِ شَىْءٌ} فَالْعَفْوُ أَنْ يَقْبَلَ الدِّيَةَ فِي الْعَمْدِ {فَاتِّبَاعٌ بِالْمَعْرُوفِ وَأَدَاءٌ إِلَيْهِ بِإِحْسَانٍ} يَتَّبِعُ بِالْمَعْرُوفِ وَيُؤَدِّي بِإِحْسَانٍ {ذَلِكَ تَخْفِيفٌ مِنْ رَبِّكُمْ} وَرَحْمَةٌ مِمَّا كُتِبَ عَلَى مَنْ كَانَ قَبْلَكُمْ {فَمَنِ اعْتَدَى بَعْدَ ذَلِكَ فَلَهُ عَذَابٌ أَلِيمٌ} قَتَلَ بَعْدَ قَبُولِ الدِّيَةِ  

"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."  

كَانَ فِي بَنِي إِسْرَائِيلَ الْقِصَاصُ وَلَمْ تَكُنْ فِيهِمُ الدِّيَةُ فَأَنْزَلَ اللَّهُ ﷻ { 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  

[Machine] "Allah has prescribed for this nation the law of retaliation in cases of murder: free man for free man, slave for slave, and female for female. But whoever is granted clemency by his brother (the victim), then it should be followed by kindness and compensation to the best of their ability. This is a relief from your Lord. It is similar to what was prescribed for those before you. And whoever transgresses after this, there shall be a painful punishment for him." [Quran 2:178]

16035 Ali ibn Abdullah narrated that Mujahid informed him that Amr ibn Dinar said: Ibn Abbas narrated to me, mentioning it in similar words.  

اللهُ ﷻ لِهَذِهِ الْأُمَّةِ {كُتِبَ عَلَيْكُمُ الْقِصَاصُ فِي الْقَتْلَى الْحُرُّ بِالْحُرِّ وَالْعَبْدُ بِالْعَبْدِ وَالْأُنْثَى بِالْأُنْثَى فَمَنْ عُفِيَ لَهُ مِنْ أَخِيهِ شَيْءٌ} [البقرة 178] قَالَ الْعَفْوُ أَنْ يَقْبَلَ الدِّيَةَ فِي الْعَمْدِ {فَاتِّبَاعٌ بِالْمَعْرُوفِ وَأَدَاءٌ إِلَيْهِ بِإِحْسَانٍ ذَلِكَ تَخْفِيفٌ مِنْ رَبِّكُمْ} [البقرة 178] مِمَّا كُتِبَ عَلَى مَنْ كَانَ قَبْلَكُمْ {فَمَنِ اعْتَدَى بَعْدَ ذَلِكَ فَلَهُ عَذَابٌ أَلِيمٌ} [البقرة 178] 16035 وَأَخْبَرَنَا عَلِيُّ بْنُ أَحْمَدَ بْنِ عَبْدَانَ أنبأ أَحْمَدُ بْنُ عُبَيْدٍ الصَّفَّارُ ثنا إِسْمَاعِيلُ بْنُ إِسْحَاقَ ثنا عَلِيُّ بْنُ عَبْدِ اللهِ ثنا سُفْيَانُ عَنْ عَمْرِو بْنِ دِينَارٍ قَالَ حَدَّثَنِي مُجَاهِدٌ عَنِ ابْنِ عَبَّاسٍ فَذَكَرَهُ بِنَحْوِهِ