سنن أبي داود

Narrated AbdulAziz ibn Umar ibn AbdulAziz:

Some people of the deputation which came to my father reported the Messenger of Allah (ﷺ) 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. AbdulAziz said: Here physician does not refer to a man by qualification. it means opening a vein, incision and cauterisation.