Musannaf Ibn Abi Shayba 35:271

Yahya ibn Sa'id narrated to us, from Muhammad ibn 'Ajlan, from Abu al-Zinad, that 'Umar ibn 'Abd al-'Aziz wrote to 'Abd al-Hamid to judge by the oath along with the witness. Abu al-Zinad said: And a sheikh of their sheikhs, or one of their elders, informed me that Shurayh judged by that.