"This man killed my brother." He said: "Go and kill him as he killed your brother." The man said to him: "Fear Allah and let me go, for that will bring you a greater reward and will be better for you and your brother on the Day of Resurrection." So he let him go. The Prophet was told about that, so he asked him about it, and he told him what he had said. He said: "Pardoning him would be better for you than what he would have done for you on the Day of Resurrection when he said: 'O Lord, ask him why he killed me."' (Using translation from Nasāʾī 4731)  

أَنَّ رَجُلًا جَاءَ إِلَى النَّبِيِّ ﷺ بِرَجُلٍ فَقَالَ إِنَّ هَذَا قَتْلَ أَخِي قَالَ «اذْهَبْ فَاقْتُلْهُ كَمَا قَتَلَ أَخَاكَ» فَقَالَ لَهُ الرَّجُلُ اتَّقِ اللهَ وَاعْفُ عَنِّي فَإِنَّهُ أَعْظَمُ لِأَجْرِكَ وَخَيْرٌ لَكَ وَلِأَخِيكَ يَوْمَ الْقِيَامَةِ قَالَ فَخَلَّى عَنْهُ فَأُخْبِرَ النَّبِيُّ ﷺ فَسَأَلَهُ فَأَخْبَرَهُ بِمَا قَالَ لَهُ قَالَ فَأَعْتَقْتَهُ أَمَا إِنَّهُ كَانَ خَيْرًا مِمَّا هُوَ صَانِعٌ بِكَ يَوْمَ الْقِيَامَةِ يَقُولُ يَا رَبِّ سَلْ هَذَا فِيمَ قَتَلَنِي؟