From Sahih Bukhari (Hadith 4764):
Narrated Sa`id bin Jubair: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-Islamic period
Reference: Bukhari 4764