Quran 4:92

وَمَا كَانَ لِمُؤۡمِنٍ أَن يَقۡتُلَ مُؤۡمِنًا إِلَّا خَطَـًٔ۬ا‌ۚ وَمَن قَتَلَ مُؤۡمِنًا خَطَـًٔ۬ا فَتَحۡرِيرُ رَقَبَةٍ۬ مُّؤۡمِنَةٍ۬ وَدِيَةٌ۬ مُّسَلَّمَةٌ إِلَىٰٓ أَهۡلِهِۦۤ إِلَّآ أَن يَصَّدَّقُواْ‌ۚ فَإِن كَانَ مِن قَوۡمٍ عَدُوٍّ۬ لَّكُمۡ وَهُوَ مُؤۡمِنٌ۬ فَتَحۡرِيرُ رَقَبَةٍ۬ مُّؤۡمِنَةٍ۬‌ۖ وَإِن ڪَانَ مِن قَوۡمِۭ بَيۡنَڪُمۡ وَبَيۡنَهُم مِّيثَـٰقٌ۬ فَدِيَةٌ۬ مُّسَلَّمَةٌ إِلَىٰٓ أَهۡلِهِۦ وَتَحۡرِيرُ رَقَبَةٍ۬ مُّؤۡمِنَةٍ۬‌ۖ فَمَن لَّمۡ يَجِدۡ فَصِيَامُ شَهۡرَيۡنِ مُتَتَابِعَيۡنِ تَوۡبَةً۬ مِّنَ ٱللهِ‌ۗ وَكَانَ ٱللَّهُ عَلِيمًا حَڪِيمً۬ا ٩٢

No believer shall kill another believer, unless it is an accident. If one kills a believer by accident, he shall atone by freeing a believing slave, and paying a compensation to the victim’s family, unless they forfeit such a compensation as a charity. If the victim belonged to people who are at war with you, though he was a believer, you shall atone by freeing a believing slave. If he belonged to people with whom you have signed a peace treaty, you shall pay the compensation in addition to freeing a believing slave. If you cannot find a slave to free, you shall atone by fasting two consecutive months, in order to be redeemed by ALLAH. ALLAH is Knower, Most Wise.