Ibn Abbas (RAA) narrated that the Messenger of Allah (ﷺ) said:
"When one of you eats, he must not wipe his hand till he licks it, or gives it to someone else to lick (such as a wife, husband, etc.)." Agreed upon. (FR)
English reference (FR): Book 16, Hadith 1486 (FR)
Arabic reference (FR): Book 16, Hadith 1442 (FR)