Surah An-Nisa' (The Women), Verse 92

وَمَا كَانَ لِمُؤْمِنٍ اَنْ یَّقْتُلَ مُؤْمِنًا اِلَّا خَطَأً وَمَنْ قَتَلَ مُؤْمِنًا خَطَأً فَتَحْرِیْرُ رَقَبَةٍ مُّؤْمِنَةٍ وَّدِیَةٌ مُّسَلَّمَةٌ اِلٰۤی اَهْلِهٖۤ اِلَّاۤ اَنْ یَّصَّدَّقُوْا فَاِنْ كَانَ مِنْ قَوْمٍ عَدُوٍّ لَّكُمْ وَهُوَ مُؤْمِنٌ فَتَحْرِیْرُ رَقَبَةٍ مُّؤْمِنَةٍ وَاِنْ كَانَ مِنْ قَوْمٍ بَیْنَكُمْ وَبَیْنَهُمْ مِّیْثَاقٌ فَدِیَةٌ مُّسَلَّمَةٌ اِلٰۤی اَهْلِهٖ وَتَحْرِیْرُ رَقَبَةٍ مُّؤْمِنَةٍ فَمَنْ لَّمْ یَجِدْ فَصِیَامُ شَهْرَیْنِ مُتَتَابِعَیْنِ تَوْبَةً مِّنَ اللّٰهِ وَكَانَ اللّٰهُ عَلِیْمًا حَكِیْمًا ۟

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.”

Quran 4:92 (Yusuf Ali Translation)