Musnad Abu Ya'la al-Mawsili 161:35

As-Salt ibn Mas'ud al-Jahdari narrated to us, 'Abd al-'Aziz ibn Muhammad narrated to us, Rabi'ah informed me, from Suhayl, from his father, from Abu Hurayrah, that the Messenger of Allah (may Allah bless him and grant him peace) judged by the oath along with the witness.