Sa'id b. Jubair reported:
'Abd al Rahman b. Abzi commanded me that I should ask Ibn 'Abbas about these two verses:" He who slays a believer intentionally his requital shall be Hell where he would abide for ever" (iv. 92). So, I asked him and he said: Nothing has abrogated it. And as for this verse:" And they who call not upon another god with Allah and slay not the soul which Allah has forbidden, except in the cause of justice" (xxv. 68), he (Ibn Abbas) said: This has been revealed in regard to the polytheists."
Reference: Sahih Muslim 3023 c
In-book reference: Book 56, Hadith 21
USC-MSA web (English) reference(deprecated numbering scheme): Book 43, Hadith 7171