﴿ 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.”

Killing is a heinous and irreversible crime. One who deliberately kills another therefore brings down upon himself the wrath of God. Such an act leaves no scope for atonement. God will reject him, and he will be rewarded with eternal hell fire. Accidental killing, however, is more leniently punished. If one unintentionally kills someone, but then, fully realizing the gravity of the crime, sincerely seeks God’s forgiveness and makes due monetary compensation, one may hope for divine clemency. One positive development arising from having faced up to the enormity of the crime is the desire for self-reform. To this end God has given man His directives. Self-punishment is a starting point and may be achieved by the observance of a continuous fast.