The Messenger of Allah ﷺ said, "When one of you eats food, he should not wipe his hand until he licks it clean himself or has it licked clean."
قال رسول الله ﷺ: إذا أكل أحدكم من الطعام فلا يمسح يده حتى يلعقها، أو يلعقها.
Bukhari narrated it in the Book of Foods (5456), and Muslim in the Book of Drinks (2031:129), both of them through Sufyan (that is, Ibn Uyayna), from Amr bin Dinar, from Ata, from Ibn Abbas, who related it.His saying, "licks it," refers to someone like a servant, a wife, children, or anyone who would not find leftover food from them repulsive.