I swear by Allah, Sahl had a misunderstanding about this tradition. The Messenger of Allah (ﷺ) wrote to the Jews: A slain man has been found amongnst you, so pay his bloodwit. They wrote (to him): Swearing by Allah fifty oaths, we neither killed him nor do we know his slayer. He said: Then the Messenger of Allah (ﷺ) himself paid his bloodwit which consisted of one hundred she-camels.
Sunan Abi Dawud Book 41, Hadith 32
← Previous Hadith A man of the Ansar was killed at Khaybar and his relatives went to the Prophet (ﷺ) and mentioned that to him. He asked: Have you two witnesses who can testify to the murderer of your friend? They replied: Messenger of Allah! there was not a single Muslim present, but only Jews who sometimes have the audacity to do even greater crimes than this. He said: Then choose fifty of them and demand that they take an oath; but they refused and the Prophet (ﷺ) paid the blood-wit himself.

Sunan Abi Dawud Book 41, Hadith 31 Next Hadith → On the authority of some men of the Ansar : The Prophet (ﷺ) said to the Jews and started with them: Fifty of you should take the oaths. But they refused (to take the oaths). He then said to the Ansar: Prove your claim. They said: Do we take the oaths without seeing, Messenger of Allah? The Messenger of Allah (ﷺ) then imposed the blood-wit on the Jews because he (the slain) was found among them.

Sunan Abi Dawud Book 41, Hadith 33