وَمَا كَانَ لِمُؤۡمِنٍ أَن يَقۡتُلَ مُؤۡمِنًا إِلَّا خَطَـٔٗاۚ وَمَن قَتَلَ مُؤۡمِنًا خَطَـٔٗا فَتَحۡرِيرُ رَقَبَةٖ مُّؤۡمِنَةٖ وَدِيَةٞ مُّسَلَّمَةٌ إِلَىٰٓ أَهۡلِهِۦٓ إِلَّآ أَن يَصَّدَّقُواْۚ فَإِن كَانَ مِن قَوۡمٍ عَدُوّٖ لَّكُمۡ وَهُوَ مُؤۡمِنٞ فَتَحۡرِيرُ رَقَبَةٖ مُّؤۡمِنَةٖۖ وَإِن كَانَ مِن قَوۡمِۭ بَيۡنَكُمۡ وَبَيۡنَهُم مِّيثَٰقٞ فَدِيَةٞ مُّسَلَّمَةٌ إِلَىٰٓ أَهۡلِهِۦ وَتَحۡرِيرُ رَقَبَةٖ مُّؤۡمِنَةٖۖ فَمَن لَّمۡ يَجِدۡ فَصِيَامُ شَهۡرَيۡنِ مُتَتَابِعَيۡنِ تَوۡبَةٗ مِّنَ ٱللَّهِۗ وَكَانَ ٱللَّهُ عَلِيمًا حَكِيمٗا

Wa maa kaana limu'minin ai yaqtula mu'minan illaa khata'aa; waman qatala mu'minan khata'an fa tahreeru raqabatim mu'minatinw wa diyatum musallamatun ilaaa ahliheee illaaa ai yassaddaqoo; fa in kaana min qawmin 'aduwwil lakum wa huwa mu'minun fa tahreeru raqabatim mu'minah; wa in kaana min qawmim bainakum wa bainahum meesaaqun fadiyatum musallamatun ilaaa ahlihee wa tahreeru raqabatim mu'minah; famal lam yajid fa Siyaamu shahraini mutataabi'aini tawbatan minal laah; wa kaanal laahu 'Aleeman hakeemaa

Never should a believer kill a believer; but (If it so happens) by mistake, (Compensation is due): If one (so) kills a believer, it is ordained that he should free a believing slave, and pay compensation to the deceased's family, unless they remit it freely. If the deceased belonged to a people at war with you, and he was a believer, the freeing of a believing slave (Is enough). If he belonged to a people with whom ye have treaty of Mutual alliance, compensation should be paid to his family, and a believing slave be freed. For those who find this beyond their means, (is prescribed) a fast for two months running: by way of repentance to Allah: for Allah hath all knowledge and all wisdom.

— An-Nisa' (ٱلنِّسَاء), 4:92