Musnad Ahmad 355:1

Hajjaj narrated to us, he said: Layth narrated to us, he said: Uqayl narrated to me, from Ibn Shihab, from Abu Salamah ibn Abd al-Rahman and Sulayman ibn Yasar, from a man of the Ansar from the companions of the Prophet, may Allah bless him and grant him peace: "That the *Qasamah* (oath-taking procedure) in the Pre-Islamic period was the *Qasamah* of blood, and the Messenger of Allah, may Allah bless him and grant him peace, upheld it as it was in the Pre-Islamic period. And the Messenger of Allah, may Allah bless him and grant him peace, judged by it between some people of the Ansar from the Banu Harithah who claimed it against the Jews."