Musannaf Ibn Abi Shayba 18:94

Abu Bakr narrated to us, he said: Abda bin Sulayman narrated to us, from Amr bin Maymun, he said: Umar bin Abd al-Aziz wrote: "There is no blood money (diya) for what is less than the *mudihah* (a wound that exposes the bone), except for the physician's fee."