﴿ وَمَا كَانَ لِمُؤْمِنٍ أَن يَقْتُلَ مُؤْمِنًا إِلَّا خَطَـًۭٔا ۚ وَمَن قَتَلَ مُؤْمِنًا خَطَـًۭٔا فَتَحْرِيرُ رَقَبَةٍۢ مُّؤْمِنَةٍۢ وَدِيَةٌۭ مُّسَلَّمَةٌ إِلَىٰٓ أَهْلِهِۦٓ إِلَّآ أَن يَصَّدَّقُوا۟ ۚ فَإِن كَانَ مِن قَوْمٍ عَدُوٍّۢ لَّكُمْ وَهُوَ مُؤْمِنٌۭ فَتَحْرِيرُ رَقَبَةٍۢ مُّؤْمِنَةٍۢ ۖ وَإِن كَانَ مِن قَوْمٍۭ بَيْنَكُمْ وَبَيْنَهُم مِّيثَٰقٌۭ فَدِيَةٌۭ مُّسَلَّمَةٌ إِلَىٰٓ أَهْلِهِۦ وَتَحْرِيرُ رَقَبَةٍۢ مُّؤْمِنَةٍۢ ۖ فَمَن لَّمْ يَجِدْ فَصِيَامُ شَهْرَيْنِ مُتَتَابِعَيْنِ تَوْبَةًۭ مِّنَ ٱللَّهِ ۗ وَكَانَ ٱللَّهُ عَلِيمًا حَكِيمًۭا ﴾

“AND IT IS not conceivable that a believer should slay another believer, unless it be by mistake. And upon him who has slain a believer by mistake there is the duty of freeing a believing soul from bondage and paying an indemnity to the victim's relations, unless they forgo it by way of charity. Now if the slain, while himself a believer, belonged to a people who are at war with you, [the penance shall be confined to] the freeing of a believing soul from bondage; whereas, if he belonged to a people to whom you are bound by a covenant, [it shall consist of] an indemnity to be paid to his relations in ad­dition to the freeing of a believing soul from bon­dage. And he who does not have the wherewithal shall fast [instead] for two consecutive months. (This is) the atonement ordained by God: and God is indeed all-knowing, wise.”

(It is not for a believer) it is not allowed for a believer, meaning here 'Ayyash Ibn Abi Rabi'ah (to kill a believer) Harith Ibn Zayd ((unless (it be) by mistake) even if it be by mistake. (He who hath killed a believer by mistake must set free a believing slave) a slave who believes in Allah and His Messenger, (and pay the blood money) in full (to the family of the slain) to the next of kin of the victim who have the right to demand retaliation, (unless they remit it as a charity) unless the next of kin of the victim remit the blood money to the killer as a charity. (If he) the victim (be of a people hostile unto you) who are at war with you, (and he) i.e. the victim (is a believer, then (the penance is) to set free a believing slave) the killer should set free a slave who believes in Allah and His Messenger and so does not have to pay the blood money. Harith belonged to a people who were at war with the Messenger of Allah (pbuh). (And if he) the victim (cometh of a folk between whom and you there is a covenant) a treaty and peace, (then the blood money must be paid) in full (unto his folk) to the next of kin of the victim (and (also) a believing slave must be set free) a slave who believes in the divine Oneness of Allah. (And whoso hath not the wherewithal) to set free a believing slave (must fast two consecutive months) continuously. (A penance from Allah) if he does this, Allah will forgive him for killing a believer by mistake. (Allah is Knower) of him who kills by mistake, (Wise) in that which he ought to do.