It is narrated from Sayyiduna Jabir (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "When any one of you eats food, he should not wipe his hand with a towel until he has licked his fingers, for he does not know in which part of his food the blessing lies."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 14390