The killer and the killed are (doomed) to fire. A person came to the other person (the heir of the deceased) and he reported to him the words of the Messenger of Allah ﷺ, and so he let him off. Isma'il b. Salim said: I made a mention of it to Habib b. Abu Thabit and he said: Ibn Ashwa' reported to me that Allah's Apostle ﷺ had asked him to pardon him, but he refused.
أُتِيَ رَسُولُ اللَّهِ ﷺ بِرَجُلٍ قَتَلَ رَجُلاً فَأَقَادَ وَلِيَّ الْمَقْتُولِ مِنْهُ فَانْطَلَقَ بِهِ وَفِي عُنُقِهِ نِسْعَةٌ يَجُرُّهَا فَلَمَّا أَدْبَرَ قَالَ رَسُولُ اللَّهِ ﷺ الْقَاتِلُ وَالْمَقْتُولُ فِي النَّارِ فَأَتَى رَجُلٌ الرَّجُلَ فَقَالَ لَهُ مَقَالَةَ رَسُولِ اللَّهِ ﷺ فَخَلَّى عَنْهُ قَالَ إِسْمَاعِيلُ بْنُ سَالِمٍ فَذَكَرْتُ ذَلِكَ لِحَبِيبِ بْنِ أَبِي ثَابِتٍ فَقَالَ حَدَّثَنِي ابْنُ أَشْوَعَ أَنَّ النَّبِيَّ ﷺ إِنَّمَا سَأَلَهُ أَنْ يَعْفُوَ عَنْهُ فَأَبَى