Noon, I'm not a teacher. I can and want to give only hints, so others can think about if they like. Sometimes hints are in one word, even one letter, sometimes they're in much broader set of letters. But, I'd try to explain to you (not to teach you) where from I got this I talked about.
If you look very start of 4:92 you'll notice that it's about a MU'MIN killing other mu'min. What is told is:
QuoteAnd it haven't happen for a MU'MIN to kill a mu'min, except (in a state of, due to accusative after) mistake...
But let's examine a word I (and many others) translated as "mistake". It's khaTa' خَطَأً. Its root talks about sins as errs/mistakes, meaning not intentional. Even without intention deeds are still sins. That person is bound by what he did.
Imagine that in a place where you live somebody plays with a gun and kills somebody without intention. Will he be free without any consequences? Or he'll be imprisoned and judged, probably not the same as if he killed with intention?
So, who needs taHreer (release, liberation, freeing) and of what? Do you think that people follow Allah's guidance if there're slaves in chains in their society?
Release OF reqaba mu'mina, why? Reqaba is a potential as khaTa' is potential, why? Both are potentials because khaTa' should be examined, if a killer had an intention to kill, and reqaba is a potential because this word means that he is potentially monitored, watched. For what? For his intention and for eventual revenge. Thus, he needs to be released of that. But why feminine? This is a great wisdom for us. This is a story of ONE MU'MIN as a killer, and reqaba is telling that it's one person monitored, as khaleefa means "one khaliph". Mu'mina is an adjective of reqaba and thus feminine, but it can be for both males and females. You can find this, for example, as 'emr waaHida (a single 'emr), even 'emr is masculine.
In any case murderer should be released. If not, then he has to "fast". For two months? Nah! But we already talked about šehr, šuhoor and ešhur. If you think that murderer who's not released of his khaTa' should fast for 2 moths I ask you for a wisdom of that, just think about it. I'll tell you why I think it's in "two open contacts".
Have you ever been so angry to somebody that you could kill him for something he done to you, and you didn't want to forgive him?
The Qur'an is not trying to make robots of us, but it's teaching us real things from our real lives. Allah knows us best and He knows what we're capable to do. He wants, as I understood, family of killed to cool down even they don't want to forgive, and a killer should ask from Allah forgiveness by regretting.
I really think that classical translations are imposing something unreal to us, and they didn't translate this good.
