Jamil bin Abi al-Mada' (may Allah have mercy on him) narrates from his father that Marwan bin al-Hakam asked Sayyiduna Zayd bin Thabit (may Allah be pleased with him): How do you eat? He replied: Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) informed me from the Messenger of Allah (peace and blessings be upon him) that he said: "When one of you eats food, let him not wipe his hand until he has licked his fingers, for he does not know in which part of his food the blessing has been placed for him."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 5415