An-Nisaa — Ruku 13

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 presented to the deceased's family [is required] unless they give [up their right as] charity. But if 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, [seeking] acceptance of repentance from Allah. And Allah is ever Knowing and Wise.

But whoever kills a believer intentionally - his recompense is Hell, wherein he will abide eternally, and Allah has become angry with him and has cursed him and has prepared for him a great punishment.

O you who have believed, when you go forth [to fight] in the cause of Allah, investigate; and do not say to one who gives you [a greeting of] peace "You are not a believer," aspiring for the goods of worldly life; for with Allah are many acquisitions. You [yourselves] were like that before; then Allah conferred His favor upon you, so investigate. Indeed Allah is ever, with what you do, Acquainted.

Not equal are those believers remaining [at home] - other than the disabled - and the mujahideen, [who strive and fight] in the cause of Allah with their wealth and their lives. Allah has preferred the mujahideen through their wealth and their lives over those who remain [behind], by degrees. And to both Allah has promised the best [reward]. But Allah has preferred the mujahideen over those who remain [behind] with a great reward -

Degrees [of high position] from Him and forgiveness and mercy. And Allah is ever Forgiving and Merciful.