Sahih al-Bukhari Book 65, Hadith 285
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."
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."
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."