Musannaf Ibn Abi Shayba 18:867

Abu Bakr narrated to us, he said: Hafs narrated to us, from Abd al-Aziz ibn Umar, he said: Some of those who came to my father narrated to me, he said: The Prophet, may Allah bless him and grant him peace, said: "Any physician who practices medicine on a people, and he was not known for medicine before that, then he causes harm (a'nata), he is liable." Abd al-Aziz said: As for it, it is not 'al-a'nat' (harm/difficulty), but rather it is cutting the veins and the abdomen.