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.

وَعَنْ اِبْنِ عَبَّاسٍ ‏-رَضِيَ اَللَّهُ عَنْهُمَا‏- قَالَ: قَالَ رَسُولُ اَللَّهِ ‏- صلى الله عليه وسلم ‏-{ إِذَا أَكَلَ أَحَدُكُمْ طَعَامًا, فَلَا يَمْسَحْ يَدَهُ, حَتَّى يَلْعَقَهَا, أَوْ يُلْعِقَهَا } مُتَّفَقٌ عَلَيْهِ.‏ [1]‏ .‏