Sayyiduna Sahl bin Abi Hathmah and Sayyiduna Rafi' bin Khadij (may Allah be pleased with them both) narrate that Muhayyisah bin Mas'ud and Abdullah bin Sahl set off towards Khaybar and separated among the palm trees, and Abdullah bin Sahl was killed. They accused the Jews. So his brother Abd al-Rahman bin Sahl and his two paternal cousins, Huwayyisah and Muhayyisah, came to the Prophet (peace and blessings be upon him). Abd al-Rahman spoke about the matter of his brother, though he was the youngest of them, so the Messenger of Allah (peace and blessings be upon him) said: "The elder, the elder", or he said: "Let the eldest begin." So the two of them spoke about the matter of their companion. The Messenger of Allah (peace and blessings be upon him) said: "Shall fifty of you swear against a man among them, and then he will be handed over to you with his rope?" They said: "It is a matter we did not witness; how can we swear?" He said: "Then the Jews will clear themselves of your claim with the oaths of fifty of them?" They said: "O Messenger of Allah, they are a disbelieving people." So the Messenger of Allah (peace and blessings be upon him) paid his blood money from his own side. Sahl said: One day I entered a pen of theirs, and a she-camel from those camels gave me a kick with her leg.
In another narration: The Messenger of Allah (peace and blessings be upon him) said: "Become entitled to your companion" — or he said: "your slain man" — "by the oaths of fifty of you." They said: "It is a matter we did not witness." He said: "Then the Jews will clear themselves of your claim with the oaths of fifty of them", and he mentioned the rest with the same meaning.
Hammad bin Zayd narrated it thus: "Fifty of you shall swear against a man", whereas the narration of the group is as has preceded, and a group is more likely to have preserved it than a single narrator.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب القسامة / 16434