Surah An-Nisa, ayah 92

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 ٩٢

Wamā kāna limu'minin an yaqtula mu'minan illā khata'an waman qatala mu'minan khata'an fatahrīru raqabatim mu'minatin wadiyatum musallamatun ilā ahlihī illā an yassaddaqū fa in kāna min qawmin 'aduwwil lakum wahuwa mu'minun fatahrīru raqabatim mu'minatin wa in kāna min qawmi baynakum wabaynahum mīthāqun fadiyatum musallamatun ilā ahlihī watahrīru raqabatim mu'minatin famal lam yajid fasiyāmu shahrayni mutatābi'ayni tawbatam minallāhi wakānallāhu 'alīman hakīmā

And never is it for a believer to kill a believer except by mistake. And whoever kills a believer by mistake - then the freeing of a believing slave and a compensation payment [diyah] presented to his [i.e., the deceased's] family [is required], unless they give [up their right as] charity. But if he [i.e., the deceased] was from a people at war with you and he was a believer - then [only] the freeing of a believing slave; and if he was from a people with whom you have a treaty - then a compensation payment presented to his family and the freeing of a believing slave. And whoever does not find [one or cannot afford to buy one] - then [instead], a fast for two months consecutively,²⁰⁹ [seeking] acceptance of repentance from Allāh.²¹⁰ And Allāh is ever Knowing and Wise.