وَمَا كَانَ لِمُؤْمِنٍ أَن يَقْتُلَ مُؤْمِنًا إِلاَّ خَطَئًا وَمَن قَتَلَ مُؤْمِنًا خَطَئًا فَتَحْرِيرُ رَقَبَةٍ مُّؤْمِنَةٍ وَدِيَةٌ مُّسَلَّمَةٌ إِلَى أَهْلِهِ إِلاَّ أَن يَصَّدَّقُواْ فَإِن كَانَ مِن قَوْمٍ عَدُوٍّ لَّكُمْ وَهُوَ مْؤْمِنٌ فَتَحْرِيرُ رَقَبَةٍ مُّؤْمِنَةٍ وَإِن كَانَ مِن قَوْمٍ بَيْنَكُمْ وَبَيْنَهُمْ مِّيثَاقٌ فَدِيَةٌ مُّسَلَّمَةٌ إِلَى أَهْلِهِ وَتَحْرِيرُ رَقَبَةٍ مُّؤْمِنَةً فَمَن لَّمْ يَجِدْ فَصِيَامُ شَهْرَيْنِ مُتَتَابِعَيْنِ تَوْبَةً مِّنَ اللّهِ وَكَانَ اللّهُ عَلِيمًا حَكِيمًا
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سورة النساء
(4/92) It is not (permissible) for a believer to kill a believer except by mistake; and whoever kills a believer by mistake, he should set free a believing slave and compensation payment should be given to the family of the slain, unless they remit the compensation payment as alms. But if he (who killed a man by mistake) is from a tribe hostile to you and he is a believer, shall free a believing slave; and if he is from a tribe between whom and you there is a covenant, the compensation should be paid to his people along with the freeing of a believing slave; but he who can not fulfill these should fast for two months successively in order to seek repentance from Allah. And Allah is All-Knowing, All-Wise.
Surah An-Nisa