Al-Hasan (al-Basri) (may Allah have mercy on him) relates: Once Sayyiduna Ma'qil bin Yasar (may Allah be pleased with him) was eating a meal when a morsel fell from him. He picked it up, cleaned off the dirt that was on it and ate it. It was said to him: May Allah set the governor right! These non-Muslims are winking at one another about your eating the fallen morsel, even though this food is placed before you. He said: "I will not abandon something I have heard for the sake of these non-Muslims. We used to be commanded that if the morsel of any of us fell, he should pick it up, clean off whatever dirt was on it and eat it, and not leave it for Satan."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17584