Mukhtasar Muslim (Abridged) 1099 — Who kills a disbeliever and remains

Abu Huraira (may Allah be pleased with him) reports that the Messenger of Allah (peace and blessings of Allah be upon him) said: Both will not be gathered together in Hell in such a way that they would harm each other. The people asked, "O Messenger of Allah! Who are those people?" He (peace be upon him) said: The Muslim who kills a disbeliever, then remains steadfast upon righteousness.