`Ali narrated that Allah's Messenger said:
«وَلَا يُقْتَلُ مُسْلِمٌ بِكَافِر»
(The Muslim is not killed for the disbeliever (whom he kills).)
No opinion that opposes this ruling could stand correct, nor is there an authentic Hadith to contradict it. However, Abu Hanifah thought that the Muslim could be killed for a disbeliever, following the general meaning of the Ayah (5:45) in Surat Al-Ma'idah (chapter 5 in the Qur'an).
The Four Imams (Abu Hanifah, Malik, Shafii and Ahmad) and the majority of scholars stated that the group is killed for one person whom they murder.Umar said, about a boy who was killed by seven men, "If all the residents of Sana' (capital of Yemen today) collaborated on killing him, I would kill them all.'' No opposing opinion was known by the Companions during that time which constitutes a near Ijma (consensus). There is an opinion attributed to Imam Ahmad that a group of people is not killed for one person whom they kill, and that only one person is killed for one person. Ibn Al-Mundhir also attributed this opinion to Muadh, Ibn Az-Zubayr,Abdul-Malik bin Marwan, Az-Zuhri, Ibn Sirin and Habib bin Abu Thabit. Allah's statement:
﴿فَمَنْ عُفِىَ لَهُ مِنْ أَخِيهِ شَىْءٌ فَاتِّبَاعٌ بِالْمَعْرُوفِ وَأَدَآءٌ إِلَيْهِ بِإِحْسَـنٍ﴾
(But if the killer is forgiven by the brother (or the relatives) of the killed (against blood money), then it should be sought in a good manner, and paid to him respectfully.) refers to accepting blood money (by the relatives of the victim in return for pardoning the killer) in cases of intentional murder. This opinion is attributed to Abu Al-Aliyah, Abu Shatha', Mujahid, Said bin Jubayr,Ata' Al-Hasan, Qatadah and Muqatil bin Hayyan. Ad-Dahhak said that Ibn `Abbas said:
﴿فَمَنْ عُفِىَ لَهُ مِنْ أَخِيهِ شَىْءٌ﴾
(But if the killer is forgiven by the brother (or the relatives) of the killed (against blood money)) means the killer is pardoned by his brother (i.e., the relative of the victim) and accepting the Diyah after capital punishment becomes due (against the killer), this is the `Afw (pardon mentioned in the Ayah).'' Allah's statement:
﴿فَاتِّبَاعٌ بِالْمَعْرُوفِ﴾
(...then it should be sought in a good manner,) means, when the relative agrees to take the blood money, he should collect his rightful dues with kindness:
﴿وَأَدَآءٌ إِلَيْهِ بِإِحْسَـنٍ﴾
( and paid to him respectfully.) means, the killer should accept the terms of settlement without causing further harm or resisting the payment.
Allah's statement:
﴿ذَلِكَ تَخْفِيفٌ مِّن رَّبِّكُمْ وَرَحْمَةٌ﴾
(This is an alleviation and a mercy from your Lord.) means the legislation that allows you to accept the blood money for intentional murder is an alleviation and a mercy from your Lord. It lightens what was required from those who were before you, either applying capital punishment or forgiving.
Said bin Mansur reported that IbnAbbas said, "The Children of Israel were required to apply the Law of equality in murder cases and were not allowed to offer pardons (in return for blood money). Allah said to this Ummah (the Muslim nation):
﴿كُتِبَ عَلَيْكُمُ الْقِصَاصُ فِي الْقَتْلَى الْحُرُّ بِالْحُرِّ وَالْعَبْدُ بِالْعَبْدِ وَالاٍّنثَى بِالاٍّنْثَى فَمَنْ عُفِىَ لَهُ مِنْ أَخِيهِ شَىْءٌ﴾
(The Law of equality in punishment is prescribed for you in case of murder: the free for the free, the servant for the servant, and the female for the female. But if the killer is forgiven by the brother (or the relatives) of the killed (against blood money),)
Hence, pardoning' orforgiving' means accepting blood money in intentional murder cases.'' Ibn Hibban also recorded this in his Sahih. Qatadah said:
﴿ذَلِكَ تَخْفِيفٌ مِّن رَّبِّكُمْ﴾
(This is an alleviation from your Lord)
Allah had mercy on this Ummah by giving them the Diyah which was not allowed for any nation before it. The People of the Torah (Jews) were allowed to either apply the penal code (for murder, i.e., execution) or to pardon the killer, but they were not allowed to take blood money. The People of the Injil (the Gospel - the Christians) were required to pardon (the killer, but no Diyah was legislated). This Ummah (Muslims) is allowed to apply the penal code (execution) or to pardon and accept the blood money.'' Similar was reported from Said bin Jubayr, Muqatil bin Hayyan and Ar-Rabi bin Anas.
Allah's statement:
﴿فَمَنِ اعْتَدَى بَعْدَ ذَلِكَ فَلَهُ عَذَابٌ أَلِيمٌ﴾
(So after this whoever transgresses the limits, he shall have a painful torment.) means, those who kill in retaliation after taking the Diyah or accepting it, they will suffer a painful and severe torment from Allah. The same was reported from Ibn Abbas, Mujahid,Ata' Ikrimah, Al-Hasan, Qatadah, Ar-Rabi bin Anas, As-Suddi and Muqatil bin Hayyan.