According to Islamic scholars, licking the plate or utensil and fingers after eating is a Sunnah. This Islamic ruling is supported by Hadith.

In a narration from Tirmidhi, Hazrat Nabisha al-Khair (RA) reported that the Prophet (peace be upon him) said that whoever eats food in a bowl or plate and then licks it clean, that utensil makes dua for his forgiveness.

علامہ خطیب شربینی (رحمہ اللہ) also stated that it is recommended (Sunnah) to lick the utensil and fingers after eating.

This fatwa clearly shows that cleaning the plate and fingers by licking them is a Sunnah practice in Islam.