Musannaf Ibn Abi Shayba 13:3036

Abu Bakr narrated to us, he said: Zayd ibn al-Hubab narrated to us, he said: Sayf ibn Sulayman al-Makki narrated to us, from Qays ibn Sa'd, from 'Amr ibn Dinar, from Ibn 'Abbas, that the Prophet (may Allah bless him and grant him peace) judged by a witness along with an oath.