The Statement of Allah the Exalted: And those who invoke not any other ilāh (God) along with Allah, nor kill such person... (V.25:68)

I or somebody, asked Allah's Messenger (ﷺ) "Which is the biggest sin in the Sight of Allah?" He said, "That you set up a rival (in worship) to Allah though He Alone created you." I asked, "What is next?" He said, "Then, that you kill your son, being afraid that he may share your meals with you." I asked, "What is next?" He said, "That you commit illegal sexual intercourse with the wife of your neighbor." Then the following Verse was revealed to confirm the statement of Allah's Messenger (ﷺ): "Those who invoke not with Allah, any other god, nor kill life as Allah has forbidden except for just cause, nor commit illegal sexual intercourse." (25.68)

That he asked Sa`id bin Jubair, "Is there any repentance of the one who has murdered a believer intentionally?" Then I recited to him:-- "Nor kill such life as Allah has forbidden except for a just cause." Sa`id said, "I recited this very Verse before Ibn `Abbas as you have recited it before me. Ibn `Abbas said, 'This Verse was revealed in Mecca and it has been abrogated by a Verse in Surat-An-Nisa which was later revealed in Medina."

The people of Kufa differed as regards the killing of a believer so I entered upon Ibn `Abbas (and asked him) about that. Ibn `Abbas said, "The Verse (in Surat-An-Nisa', 4:93) was the last thing revealed in this respect and nothing cancelled its validity."

I asked Ibn `Abbas about Allah's saying:-- '.. this reward is Hell Fire.' (4.93) He said, "No repentance is accepted from him (i.e. the murderer of a believer)." I asked him regarding the saying of Allah: 'Those who invoke not with Allah any other god.'...(25.68) He said, "This Verse was revealed concerning the pagans of the pre-lslamic period."