Ibn Ka'b b. Malik reported on the authority of his father that the Messenger of Allah ﷺ used to eat (food) with three fingers and he licked his hand before wiping it (with towel). (Using translation from Muslim 2032b)   

كَانَ رَسُولُ اللهِ ﷺ يَأْكُلُ بِثَلَاثِ أَصَابِعَ وَيَلْعَقُ يَدَهُ قَبْلَ أَنْ يَمْسَحَهَا  

When one of you eats, he must not wipe his hand with a handkerchief till he licks it or gives it to someone to lick. (Using translation from Abū Dāʾūd 3847)   

قَالَ رَسُولُ اللهِ ﷺ إِذَا أَكَلَ أَحَدُكُمْ طَعَامًا فَلَا يَمْسَحْ يَدَهُ حَتَّى يَلْعَقَهَا أَوْ يُلْعِقَهَا  

[Machine] The Prophet of Allah ﷺ said, "When one of you eats food, let him not wipe his hand until he licks it or someone else licks it."  

قَالَ رَسُولُ اللهِ ﷺ إِذَا أَكَلَ أَحَدُكُمْ مِنَ الطَّعَامِ فَلَا يَمْسَحْ يَدَهُ حَتَّى يَلْعَقَهَا أَوْ يُلْعِقَهَا