Musannaf Ibn Abi Shaybah 39195 — The time of Isha: Abu Hanifah said

Sa'id (bin al-Musayyib) said that Qasamah (the oath procedure in cases of unresolved killing) existed (even) in the pre-Islamic era, and the Prophet (peace and blessings be upon him) upheld it in the case of a man of the Ansar who was found (slain) in a well of the Jews. The narrator said: The Prophet (peace and blessings be upon him) began with the Jews, and he (peace and blessings be upon him) required fifty oaths of them. The Jews said: "We will never swear." Then the Prophet (peace and blessings be upon him) said to the Ansar: "Will you swear?" The Ansar said: "We will never swear." So the Prophet (peace and blessings be upon him) placed the blood money of that slain man upon the Jews, because he had been killed among them.