Abdullah bin Abbas reported,
Someone asked Ibn Abbas about a person who deliberately kills a believer, then repents, believes, does righteous deeds, and follows guidance.He replied, "Woe to him! How can guidance be available to him? I heard your Prophet ﷺ say, 'On the Day of Resurrection, the killer and his victim will come forth, the victim clinging to the head of his killer, saying, "My Lord, ask this man why he killed me."' By Allah, Allah 
revealed this verse to your Prophet, and He never abrogated it after revealing it."
Ibn Majah 2621
Sahihحدثنا محمد بن الصباح حدثنا سفيان بن عيينة عن عمار الدهني عن سالم بن أبي الجعد قال
سئل ابن عباس
عمن قتل مؤمنا متعمدا ثم تاب وآمن وعمل صالحا ثم اهتدى قال ويحه وأنى له الهدى سمعت نبيكم ﷺ يقول يجيء القاتل والمقتول يوم القيامة متعلق برأس صاحبه يقول رب سل هذا لم قتلني والله لقد أنزلها الله عز وجل على نبيكم ثم ما نسخها بعدما أنزلها
Its isnad is sahih. Nasai reported it in the chapter on the prohibition of blood and the gravity of bloodshed, no. 4004, 4870. Reference: also Humaydi, no. 488, from the hadith of Sufyan through the same route, and Yahya bin Abdullah bin Harith al-Mujabbir al-Taymi followed him in it, as found in Ahmad, 1/240, 294, 364, and elsewhere, though he is lenient in hadith transmission (Taqrib).This hadith has corroborating reports in Bukhari, no. 3855, Muslim, no. 3023, Nasai, 7/84, and Tirmidhi, no. 2208, where he said, hasan sahih, gharib, and no. 3029, where he said, hasan, gharib, and others, and through these the hadith is confirmed as sahih.