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.
Hadiths 4867https://sunnah.com/nasai:4867
أَخْبَرَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالَ أَنْبَأَنَا النَّضْرُ بْنُ شُمَيْلٍ، قَالَ حَدَّثَنَا شُعْبَةُ، عَنْ عُبَيْدِ اللَّهِ بْنِ أَبِي بَكْرٍ، قَالَ سَمِعْتُ أَنَسًا، يَقُولُ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ح وَأَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ الأَعْلَى قَالَ حَدَّثَنَا خَالِدٌ قَالَ حَدَّثَنَا شُعْبَةُ عَنْ عُبَيْدِ اللَّهِ بْنِ أَبِي بَكْرٍ عَنْ أَنَسٍ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " الْكَبَائِرُ الشِّرْكُ بِاللَّهِ وَعُقُوقُ الْوَالِدَيْنِ وَقَتْلُ النَّفْسِ وَقَوْلُ الزُّورِ " .
It was narrated that 'Ubaidullah bin abi Bakr said: "I heard Ana's say: 'The Messenger of Allah said: 'the major sins are; associating others with Allah (shirk), disobeying one's parents, killing a soul (murder) and speaking falsely.
It was narrated from 'Abdullah bin 'Amr that the Prophet said: "The major sins are: associating others with Allah, disobeying parents, killing a souls (murder) and swearing a false oath knowingly.
It was narrated that Ibn 'Abbas said: "The Messenger of Allah said: 'No one who commits Zina is a believer at the moment when he is committing Zina, and no one who drinks wine is a believer at the moment when he is drinking it, and no thief is a believer at the moment when he is stealing, and no killer is a believer at the moment he is killing