Musannaf Ibn Abi Shayba 28:604

Humaid ibn Abd al-Rahman narrated to us, from a sheikh from the people of Medina, a freed slave of the Banu Abd al-Ashhal, from Dawud, from Ikrimah, from Ibn Abbas, that the Prophet, peace and blessings of Allah be upon him, used to say when he sent out his armies: "Do not kill the occupants of the hermitages."