Ka'b bin Malik (May Allah be pleased with him) reported:
I saw Messenger of Allah (ﷺ) eating with three fingers (i.e., the thumb, the index finger and the middle finger) and licking them after having finished the food.[Muslim]. (JA)
App reference (JA): Book 3, Hadith 22 (JA)
Arabic/English book reference (JA): Book 3, Hadith 749 (JA)