Musnad Abu Ya'la al-Mawsili 152:106

On the authority of al-A’mash, from ‘Umarah, from al-Aswad, who said: ‘Abdullah said: "Let not one of you assign to the Shaytan a portion of himself, by thinking that it is a duty upon him to turn away from his right side. For I have indeed seen the Messenger of Allah (may Allah bless him and grant him peace) turning away from his left side most of the time." ‘Umarah said: So I came to Medina and I saw the places of the Messenger of Allah (may Allah bless him and grant him peace) to his left.