The Prophet ﷺ used to lick his three fingers after eating, and he said, "If a morsel falls from one of you, let him remove any dirt from it and eat it, and not leave it for the devil. And let one of you wipe the dish clean, for you do not know in which part of your food the blessing lies."
حدثنا عبد الرحمن حدثنا حماد بن سلمة عن ثابت
أن النبي ﷺ كان يلعق أصابعه الثلاث إذا أكل وقال إذا وقعت لقمة أحدكم فليمط عنها الأذى وليأكلها ولا يدعها للشيطان وليسلت أحدكم الصحفة فإنكم لا تدرون في أي طعامكم البركة
Its isnad is sahih. Abdul-Rahman is Ibn Mahdi, and the hadith has previously appeared without the mention of scraping the plate in 11903.This hadith combines humility, economy, wise management, and the vexation of Satan all in a single expression. Yet many Muslims today disdain to scrape their plates and lick their fingers, throwing half their food into the garbage, and what we are experiencing now is a punishment for this.