Verses 92-93 of Chapter 4:

It does not behoove a Believer to slay another Believer except by error, and if one slays a Believer by error, he must set free one believing slave as expiation and pay blood-money to the heirs of the slain person unless they charitably forego it. But if the murdered Muslim belonged to a people who are at enmity with you, then the expiation shall be the freeing of one believing slave; and if the slain person belonged to a non-Muslim ally of yours, then the blood-money must be paid to his heirs and a believing slave has to be set free. But if one could not afford a slave, then he must fast two consecutive months. This is the way enjoined by Allah for repentance; Allah is All-Knowing, All-Wise. As regards the one who kills a Believer willfully, his recompense is Hell, wherein he shall live for ever. He has incurred Allah's wrath and His curse is on him, and Allah has prepared a woeful torment for him.