Wasting Food
Jabir (may Allah be pleased with him) reported:
Messenger of Allah (may Allah’s peace be upon him) commanded the licking of fingers and the gleaning of the dish, saying:
“You do not know in which portion the blessing lies.”
[Muslim]
Commentary from Riyad-us-Saliheen: This Hadith underlines the wisdom behind licking the fingers and the vessel. The eater never knows whether a blessing underlies what has been eaten by him, or the particles sticking to his fingers and vessels contain it. Those particles, therefore, should not be wasted; they should be made part of food by being licked. They may be invested with a blessing and proved more useful for the eater’s health and strength. Moreover, by this way he escapes disregarding the Bounty of Allah.
[Riyad-us-Saliheen; Chapter 109, #750. Dar-us-Salaam]
Muslim Manners 
I watend to spend a minute to thank you for this.