Abu Dawud Book 34, Hadith Number 4570.
Chapter : On a man who practises medicine without having its knowledge and does harm to the patient.
Narated By Some people : Abdul Aziz ibn Umar ibn Abdul Aziz said: Some people of the deputation which came to my father reported the Apostle of Allah (PBUH) as saying: Any physician who practises medicine when he was not known as a practitioner before that and he harms (the patients) he will be held responsible.
Abd al-‘Aziz said: Here physician does not refer to a man by qualification. It means opening a vein, incision and cauterization.