Musnad Abu Ya'la al-Mawsili 109:248

Abu Khaythama narrated to us, Rawh narrated to us, Ibn Jurayj narrated to us, he said: Abu al-Zubayr informed me that he heard Jabir, that he heard the Messenger of Allah (may Allah bless him and grant him peace) saying: "If one of you eats and his morsel falls from his hand, let him remove what is upon it of harm, then let him eat it, and let him not leave it for the Shaytan. For the person does not know in which part of his food the blessing is for him."