Riyad as-Salihin, Book 3, Hadith 751 (In-Book) ⓘ

Jabir (May Allah be pleased with him) reported: Messenger of Allah said, "When a morsel of any of you falls, he should pick it up and remove any of the dirt on it and then eat it, and should not leave it for Satan nor should wipe his hand with towel until he has licked his fingers, for he does not know in what portion of the food the blessing lies."[Muslim].

وعنه أن رسول الله صلى الله عليه وسلم قال‏:‏ ‏ "‏إذا وقعت لقمة أحدكم، فليأخذها فليمط ما كان بها من أذى وليأكلها، ولا يدعها للشيطان، ولا يمسح يده بالمنديل حتى يلعق أصابعه؛ فإنه لا يدرى في أي طعامه البركة‏" ‏ ‏.‏