Hazrat Abdul Aziz bin Umar narrates that those people who had come to my father told me that the Holy Prophet, peace and blessings be upon him, said: Every healer who treated a people while he had no prior knowledge of treatment, and thus worsened the illness, then that person will be held liable. Abdul Aziz says that this liability is not for the diagnosis of the illness, but rather for cutting veins and making incisions.