How can repentance be available to him? I heard your Prophet ﷺ say, "He will come holding fast to his killer, his veins gushing with blood, and he will say, 'My Lord, ask this man why he killed me.'"Then he said, "By Allah, Allah revealed this verse, and He never abrogated it."
أخبرنا قتيبة قال حدثنا سفيان عن عمار الدهني عن سالم بن أبي الجعد أن ابن عباس سئل عمن قتل مؤمنا متعمدا ثم تاب وآمن وعمل صالحا ثم اهتدى
وأنى له التوبة سمعت نبيكم ﷺ يقول يجيء متعلقا بالقاتل تشخب أوداجه دما فيقول أي رب سل هذا فيم قتلني ثم قال والله لقد أنزلها الله ثم ما نسخها
[Sahih] Ibn Majah narrated it in the Book of Blood Money, in the chapter "Is there repentance for one who kills a believer," no. 2621, from the hadith of Sufyan bin Uyayna, transmitted through him, and he explicitly stated that he heard it directly, and it is found in al-Kubra, no. 3462. The hadith has corroborating narrations in Bukhari, no. 3855, and Muslim, no. 3023, and others.