سنن النسائي

It was narrated that Wa'il said: "I saw the Messenger of Allah (ﷺ) [SAW] when a killer was brought by the heir of the victim by a string. The Messenger of Allah (ﷺ) [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 (ﷺ) [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."