An-Nisa 4:92 وما كان لمومن ان يقتل مومنا الا خطا ومن قتل مومنا خطا فتحرير رقبة مومنة ودية مسلمة الى اهله الا ان يصدقوا فان كان من قوم عدو لكم وهو مومن فتحرير رقبة مومنة وان كان من قوم بينكم وبينهم ميثاق فدية مسلمة الى اهله وتحرير رقبة مومنة فمن لم يجد فصيام شهرين متتابعين توبة من الله وكان الله عليما حكيما ٩٢

It is not for a believer (Muslim) to kill any believer, except by mistake. Whoever kills a believer by mistake, then, a believing slave has to be freed, and the blood money must be paid to his family, unless they forgo it.If he (the victim) belongs to a people hostile to you and is a believer, then, a believing slave has to be freed. If he (the victim) belongs to a people between whom and you there is treaty, then, blood money is to be paid to his family, and a believing slave to be freed. Whoever does not find one has to fast for two consecutive months. This is repentance prescribed from Allah’s side. Allah is All-Knowing, All-Wise.