Al-Muthanna Abu Jubayr (may Allah have mercy on him) narrates that Abd al-Malik bin Marwan sent a messenger to Sayyiduna Zayd bin Thabit (may Allah be pleased with him) and asked him: How do you eat and drink? He said: I drink until my breath runs out, then I take the vessel away from my mouth; and when I eat, I lick my fingers, for I heard the Messenger of Allah (peace and blessings be upon him) say: "When one of you eats, let him lick his fingers, for he does not know in which part of his food the blessing lies."
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 4899