It is narrated from Abd al-Rahman bin Bujayd bin Qayzi, of Banu Harithah — Ibn Ibrahim said: By Allah, Sahl (may Allah be pleased with him) was not more knowledgeable than him, but he was older than him — that he said to him: By Allah, the matter was not like this; rather, Sahl (may Allah be pleased with him) was mistaken. The Messenger of Allah (peace and blessings be upon him) did not say: "Swear to what you have no knowledge of." Rather, when the Ansar (may Allah be pleased with them) spoke to him, he (peace and blessings be upon him) wrote to the Jews of Khaybar: "A slain man has been found among you, between your houses, so pay his blood money." They wrote back to him, swearing by Allah that they had not killed him and did not know who his killer was. So the Messenger of Allah (peace and blessings be upon him) paid his blood money from his own funds.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب القسامة / 16439