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  

his father told them that a man who had killed another man was brought to the Prophet and he handed him over to their of the victim to kill him. Then the Prophet said to those who were sitting with him: "The killer and the slain will both be in Fire. "A man went after him and told him that, and when he told him that, he left him (let him go). He (the narrator) said: "I saw him dragging his string when he let him go. I mentioned that the Habib and he said: 'Sa'eed bin Ashwa' told me that the Prophet commanded the man to forgive him."'  

أَنَّ النَّبِيَّ ﷺ أُتِيَ بِرَجُلٍ قَدْ قَتَلَ رَجُلاً فَدَفَعَهُ إِلَى وَلِيِّ الْمَقْتُولِ يَقْتُلُهُ فَقَالَ النَّبِيُّ ﷺ لِجُلَسَائِهِ الْقَاتِلُ وَالْمَقْتُولُ فِي النَّارِ قَالَ فَاتَّبَعَهُ رَجُلٌ فَأَخْبَرَهُ فَلَمَّا أَخْبَرَهُ تَرَكَهُ قَالَ فَلَقَدْ رَأَيْتُهُ يَجُرُّ نِسْعَتَهُ حِينَ تَرَكَهُ يَذْهَبُ فَذَكَرْتُ ذَلِكَ لِحَبِيبٍ فَقَالَ حَدَّثَنِي سَعِيدُ بْنُ أَشْوَعَ قَالَ وَذَكَرَ أَنَّ النَّبِيَّ ﷺ أَمَرَ الرَّجُلَ بِالْعَفْوِ