COMMENTARY on 4:92
A. Yusuf Ali:

Translation:
Never should a believer kill a believer; but (If it so happens) by mistake, 611 (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 you 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 have all knowledge and all wisdom.
Commentary:

611  Life is absolutely sacred in the Islamic Brotherhood. But mistakes will sometimes happen, as did happen in the melee at Uhud, when some Muslims were killed (being mistaken for the enemy) by Muslims. There was no guilty intention: therefore there was no murder. But all the same, the family of the deceased was entitled to compensation unless they freely remitted it, and in addition it was provided that the unfortunate man who made the mistake should free a believing slave. Thus a deplorable mistake was made the occasion for winning the liberty of a slave who was a Believer, for Islam discountenances slavery. The compensation could only be paid if the deceased belonged to a Muslim society or to some people at peace with the Muslim society. Obviously it could not be paid if, though the deceased was a Believer, his people were at war with the Muslim society; even if his people could be reached, it is not fair to increase the resources of the enemy. If the deceased was himself an enemy at war, obviously the laws of war justify his being killed in warfare unless he surrendered. If the man who took life unintentionally has no means from which to free a believing slave or to give compensation, he must still by an act of strict self-denial (fasting for two whole months running) show that he is cognizant of the grave nature of the deed he has done and sincerely repentant I take this to apply to all three cases mentioned: that is, where a Believer killed a Believer unintentionally and the deceased (1} belonged to the same community as you, or (2) belonged to a community at war with you, or (5) belonged to a community in alliance with you.

 

Muhammad Asad:

Translation:
AND IT IS not conceivable that a believer should slay another believer, unless it be by mistake. 114 And upon him who has slain a believer by mistake there is the duty of freeing a believing soul from bondage and paying an indemnity to the victim's relations, 115 unless they forgo it by way of charity. Now if the slain, while himself a believer, belonged to a people who are at war with you, 116 [the penance shall be confined to] the freeing of a believing soul from bondage; whereas, if he belonged to a people to whom you are bound by a covenant, [it shall consist of] an indemnity to be paid to his relations in ad­dition to the freeing of a believing soul from bon­dage. 117 And he who does not have the wherewithal shall fast [instead] for two consecutive months. 118 (This is) the atonement ordained by God: and God is indeed all-knowing, wise.
Commentary:
114  On the strength of this verse, read in conjunction with verse 93, some of the Mu'tazilite scholars are of the opinion that a believer who deliberately kills another believer must be considered an unbeliever (Razi). This does not, of course, apply to the execution of a death sentence passed in due process of law.
115  Lit., "his people" - i.e., the heirs or dependants of the victim. The "freeing of a believing soul from bondage", mentioned three times in this verse, refers in the first instance to persons who have been taken captive in war (cf surah 8, note 72) But see also note 5 on 58:3.
116  Lit., "who are hostile to you" - implying that they are in an actual state of war.
117  This relates to cases where the victim is a non-Muslim belonging to a people with whom the Muslims have normal, peaceful relations; in such cases the penalty is the same as that imposed for the killing, under similar circumstances, of a fellow-believer.
118  I.e., in the way prescribed for fasting during the month of Ramadan (see 2:183-187). This alleviation applies to a person who cannot afford to pay the indemnity and/or purchase the freedom of a slave (Razi), or cannot find a slave to be freed, as may be the case in our times (Manar V, 337).