Anas (May Allah be pleased with him) reported: When the Messenger of Allah (PBUH) finished eating his food, he would lick his three fingers (i.e., the forefinger, the middle finger and the thumb). He (PBUH) said, "If anyone of you drops a morsel, he should remove anything harmful from it and then eat it. He should not leave it for Shaitan.'' He commanded us to clean out the dish saying, "You do not know in what portion of your food the blessing lies.''
[Muslim].

Commentary: This Hadith also stresses humbleness, simplicity and regard for the Blessings of Allah. To be unwilling to pick up a fallen morsel and eat it and to keep from cleaning up the dish is the style of arrogant and wealthy people. It displays disregard for Allah's Blessing. To eat the fallen morsel after cleaning it and to lick up the dish shows, apart from humbleness, regard for the Divine gift. Such an act pleases Allah. In it there is another advantageous aspect. Man never knows which is the blessed portion of food. When one licks up the dish, or even his fingers, picks up the fallen morsel and eats it after cleaning it, nothing will be wasted from the meal. In this way, the blessed portion of meal will automatically come to him and he will not remain deprived of it. Moreover, the Hadith tells us that Allah's Blessing, in whatever small quantity it may be, must not be wasted. Yet unfortunately, as we see today, food is wasted like anything in the feasts and marriage ceremonies. Whereas there are countless people in the world who do not get enough to eat, and there are many areas where people simply starve. May Allah guide us!