Murder
The fifth Greater Sin is the murder of that person whose execution has not been ordered by Allah (S.w.T.) and the Holy Prophet (S). Traditions which confirm that murder is a Greater Sin have already been mentioned at the beginning. Moreover the verses of the Holy Qur’an mention clearly the Divine punishment for the murderers.
“And whoever kills a believer intentionally, his punishment is Hell; he shall abide in it, and Allah will send His wrath on him and curse him and prepare for him a painful chastisement.”(Surah an-Nisā’ 4:93)
Five types of punishments have been ordained for those who kill the believers. First, Hell; Second, Eternal abode in Hell; Third, involvement in the Divine wrath; Fourth, being the accursed by Allah (S.w.T.); Fifth, the Great Chastisement.
Permanent Chastisement is Exclusively For unbelievers
One of the beliefs of the Shia Ithna Ashari school of thought is that eternal punishment is only for the Kuffar (Unbelievers). In other words, if a person dies in belief, he will not remain under punishment forever, even if he has killed a believer (or someone else whose killing has been prohibited according to the Divine command), or even though he has committed other greater sins. Hence the verse mentioned above has been explained in various ways. One possible explanation is that: one becomes eligible for eternal punishment only if he murders the believer because of his Imān (belief). If such is the case, then, the killer is indeed liable for everlasting chastisement, for he considered the murder of a Mu’min as Halāl, whereas it is Harām. To consider a murder of a believer Harām is an article of faith. Consequently one who does not have this belief is a Kafir.
The Life and Property of a Muslim are Protected
The Holy Prophet (S) announced on the occasion of the Farewell Pilgrimage (
Hajjatul Wida’):
“O People! It is not permitted to kill the Muslims. Similarly to appropriate their property is not allowed. So do not be unjust upon yourselves and do not revert to disbelief after my death.”
1
Another explanation of the afore-mentioned hadith is that “abide in Hell” denotes being under punishment for a very long period. It does not mean that the sinner will be involved in eternal chastisement.
https://www.al-islam.org/greater-si...yn-dastghaib-shirazi/fifth-greater-sin-murder