أَخْبَرَنَا مُحَمَّدُ بْنُ بَشَّارٍ، قَالَ حَدَّثَنَا يَحْيَى بْنُ سَعِيدٍ، عَنْ عَوْفٍ، قَالَ حَدَّثَنِي حَمْزَةُ أَبُو عُمَرَ الْعَائِذِيُّ، قَالَ حَدَّثَنَا عَلْقَمَةُ بْنُ وَائِلٍ، عَنْ وَائِلٍ، قَالَ شَهِدْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم حِينَ جَاءَ بِالْقَاتِلِ يَقُودُهُ وَلِيُّ الْمَقْتُولِ فِي نِسْعَةٍ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم لِوَلِيِّ الْمَقْتُولِ ‏"‏ أَتَعْفُو ‏"‏ ‏.‏ قَالَ لاَ ‏.‏ قَالَ ‏"‏ فَتَأْخُذُ الدِّيَةَ ‏"‏ ‏.‏ قَالَ لاَ ‏.‏ قَالَ ‏"‏ فَتَقْتُلُهُ ‏"‏ ‏.‏ قَالَ نَعَمْ ‏.‏ قَالَ ‏"‏ اذْهَبْ بِهِ ‏"‏ ‏.‏ فَلَمَّا ذَهَبَ فَوَلَّى مِنْ عِنْدِهِ دَعَاهُ فَقَالَ ‏"‏ أَتَعْفُو ‏"‏ ‏.‏ قَالَ لاَ قَالَ ‏"‏ فَتَأْخُذُ الدِّيَةَ ‏"‏ ‏.‏ قَالَ لاَ ‏.‏ قَالَ ‏"‏ فَتَقْتُلُهُ ‏"‏ ‏.‏ قَالَ نَعَمْ ‏.‏ قَالَ ‏"‏ اذْهَبْ بِهِ ‏"‏ ‏.‏ فَلَمَّا ذَهَبَ فَوَلَّى مِنْ عِنْدِهِ دَعَاهُ فَقَالَ ‏"‏ أَتَعْفُو ‏"‏ ‏.‏ قَالَ لاَ ‏.‏ قَالَ ‏"‏ فَتَأْخُذُ الدِّيَةَ ‏"‏ ‏.‏ قَالَ لاَ ‏.‏ قَالَ ‏"‏ فَتَقْتُلُهُ ‏"‏ ‏.‏ قَالَ نَعَمْ ‏.‏ قَالَ ‏"‏ اذْهَبْ بِهِ ‏"‏ ‏.‏ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم عِنْدَ ذَلِكَ ‏"‏ أَمَا إِنَّكَ إِنْ عَفَوْتَ عَنْهُ يَبُوءُ بِإِثْمِهِ وَإِثْمِ صَاحِبِكَ ‏"‏ ‏.‏ فَعَفَا عَنْهُ وَتَرَكَهُ فَأَنَا رَأَيْتُهُ يَجُرُّ نِسْعَتَهُ ‏.‏

It was narrated that Wa'il said: "I saw the Messenger of Allah [SAW] when a killer was brought by the heir of the victim by a string. The Messenger of Allah [SAW] said to the heir of the victim: 'Will you forgive him?' He said: 'No.' He said: 'Will you accept the Diyah?' He said: 'No.' He said: 'Will you kill him?' He said: 'Yes.' He said: 'Take him away.' When he went and turned away from him, he called him back and said: 'Will you forgive him?' He said: 'No.' He said: 'Will you accept the Diyah?' He said: 'No.' He said: 'Will you kill him?' He said: 'Yes.' He said: 'Take him away.' When he went and turned away from him, he called him back and said: 'Will you forgive him?' He said: 'No.' He said: 'Will you accept the Diyah?' He said: 'No.' He said: 'Will you kill him?' He said: 'Yes.' He said: 'Take him away.' At that point the Messenger of Allah [SAW] said: 'But if you forgive him, he will carry his own sin and the sin of your companion.' So he forgave him, and I saw him dragging his string." Translation Not Available

Book reference: Sunan An Nisai Book 49 Hadith 5415
Web reference: Sunan An Nisai Volume 6 Book 49 Hadith 5417