Sunan an-Nasa'i 4866

It was narrated from Salim bin abi Ja'd that:Ibn 'Abbas was asked about someone who killed a believer deliberately then he repented, believed and did righteous deeds, and followed true guidance. Ibn 'Abbas said: "There is no way he could repent! I heard your Prophet say; He (the victim) will come hanging onto his killer with his jugular veins flowing with blood and saying: "Ask him why he killed me." Then he said: "by Allah, Allah revealed it and never abrogated anything of it