How to understand verses 4:92 and 2:178

Question

O you who have believed, prescribed for you is legal retribution for those murdered – the free for the free, the slave for the slave, and the female for the female...(2:178)

The law of retribution is established here.

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 [diyah] presented to his [i.e., the deceased's] family [is required], unless they give [up their right as] charity. But if he [i.e., 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. ([4] An-Nisa : 92)

And here the murder of a believer is allowed only by mistake.

That is, in fact, it follows from the text that verse 4:92 cancels verse 2:178 in relation to Muslims. In other words, a Muslim can only be killed by mistake, and therefore it follows from the text that qisas or the execution of Muslims for any crime is prohibited.

But the interpretations of the Koran tell us the opposite: that verse 2:178 also applies to Muslims and that a Muslim should be executed for killing another Muslim. I know that this principle of retribution is correct, but I cannot understand why then 4:92 says that a Muslim can only be killed by mistake.

My question is: How to explain that verse 4:92 does not cancel verse 2:178 in relation to Muslims?

Answer 1

Prophet's definition of Muslim is

The Prophet (ﷺ) said, "A Muslim is the one from whose tongue and hands the Muslims are safe; and a Muhajir (Emigrant) is the one who refrains from what Allah has forbidden". https://sunnah.com/riyadussalihin:211

So a muslim will never kill another muslim intentionally. So if someone kills then he is not a true muslim as per the above definition. So the rule of law, that is Qisas need to be applied. But the victims relatives can always forgive him.

Another case is when two armies fight each other and there are muslims in either side, then the muslim soldier do not have option except to fight and in that way he may be killing another muslim in the enemy side. So in that case, as in the Quran verse you noted 4:92, you have to give compensation and free a slave, if not possible, have to fast 2 months consecutively