Sunan Abi Dawud Book 28, Hadith 109
when a fly alights in anyone’s vessel, he should plunge it all in, for in one of its wings there is a disease, and in the other is a cure. It prevents the wing of it is which there is a cure, so plunge it all in (the vessel).
The tradition mentioned above (No. 3833) has also been transmitted by Ibn Abbas from Maymunah, from the Prophet (ﷺ) like the tradition narrated by az-Zuhri, from Ibn al-Musayyab.
If the morsel of one of you falls down, he should wipe away anything injurious on it and eat it and not leave it for the devil. And he ordered us to clean the dish, for one of you does not leave it for the devil. And he ordered us to clean the dish, for one of you does not know in what part of his food the blessing lies.