Musnad Ahmed: Hadith 1940

Ibn "Abbas was asked about a man who killed a believer, then he repented and believed and did righteous deeds, then followed true guidance. He said: Woe to you, how could he follow true guidance? I heard your Prophet (ﷺ) say: "The slain one will come, holding on to his killer, saying: "O Lord, ask this one why he killed me." By Allah, Allah revealed it to your Prophet (ﷺ) and He did not abrogate it after He revealed it. Woe to you, how can he follow true guidance?