Musannaf Ibn Abi Shayba 13:2142

Abu Bakr narrated to us, he said: Ibn Idris narrated to us, from his father, who said: I saw Muharib ibn Dithar, Hammad, and al-Hakam. One of them was on his right and the other was on his left. He would look at al-Hakam once and at Hammad once, while the litigants were before him.