I was with the Prophet ﷺ when a man was brought who had killed someone, with a leather rope around his neck. The Prophet ﷺ called the murdered man's guardian and asked, "Will you pardon him?"He said, "No."The Prophet ﷺ asked, "Will you accept blood-money?"He said, "No."The Prophet ﷺ asked, "Will you kill him then?"He said, "Yes."The Prophet ﷺ said, "Take him."When he turned to leave, the Prophet ﷺ called him back and asked, "Will you pardon him?"He said, "No."The Prophet ﷺ asked, "Will you accept blood-money?"He said, "No."The Prophet ﷺ asked, "Will you kill him then?"He said, "Yes."The Prophet ﷺ said, "Take him."On the fourth time, the Prophet ﷺ said, "Know that if you pardon him, he will bear his own sin and the sin of your companion."So he pardoned him. The narrator said, "I saw him afterward dragging the leather rope behind him."
حدثنا عبيد الله بن عمر بن ميسرة الجشمي حدثنا يحيى بن سعيد عن عوف حدثنا حمزة أبو عمر العائذي حدثني علقمة بن وائل
كنت عند النبي ﷺ إذ جيء برجل قاتل في عنقه النسعة قال فدعا ولي المقتول فقال أتعفو قال لا قال أفتأخذ الدية قال لا قال أفتقتل قال نعم قال اذهب به فلما ولى قال أتعفو قال لا قال أفتأخذ الدية قال لا قال أفتقتل قال نعم قال اذهب به فلما كان في الرابعة قال أما إنك إن عفوت عنه يبوء بإثمه وإثم صاحبه قال فعفا عنه قال فأنا رأيته يجر النسعة
Muslim narrated it in the Book of Qasamah and Combatants, chapter on the validity of confessing to murder and enabling the victim's guardian etc., hadith 1680, from the hadith of Alqama bin Waail, and Nasai, hadith 4728, from the hadith of Yahya bin Saeed Qattan with the same chain.