Sahih Muslim | Book 23 | Hadith Number 5046

Narrated by Jabir
Jabir reported: I heard Allah's Apostle (may peace be upon him) as saying: The Satan is

present with any one of you in everything he does; he is present even when he eats food; so if any one of you drops a mouthful he should remove away anything filthy on it and eat it and not leave for the devil; and when he finishes (food) he should lick his fingers, for he does not know in what portion of his food the blessing lies.