A man from the Ansar was found killed at Khaybar. His relatives went to the Prophet ﷺ and reported the matter to him.He asked, "Do you have two witnesses who can testify to the killing of your companion?"They replied, "Messenger of Allah, there was no one there from among the Muslims. They are only Jews, and they may dare to do something even greater than this."He said, "Then choose fifty of them and have them swear an oath."But they refused, so the Prophet ﷺ paid the blood-money for him from his own resources.
حدثنا الحسن بن علي بن راشد أخبرنا هشيم عن أبي حيان التيمي حدثنا عباية بن رفاعة
أصبح رجل من الأنصار مقتولا بخيبر فانطلق أولياؤه إلى النبي ﷺ فذكروا ذلك له فقال لكم شاهدان يشهدان على قتل صاحبكم قالوا يا رسول الله لم يكن ثم أحد من المسلمين وإنما هم يهود وقد يجترئون على أعظم من هذا قال فاختاروا منهم خمسين فاستحلفوهم فأبوا فوداه النبي ﷺ من عنده
No references are available.
[Sahih] Tabarani narrated it in Al-Kabir: 4/277, no. 4413, from the hadith of Hasan bin Ali, and the hadith has very many corroborating narrations.