When anyone of you eats food, let him not wipe his hand until he licks it or has it licked.

The Prophet (may Allah's peace and blessings be upon him) ordered whoever eats not to wipe his hand or wash it until he licks it or has it licked. The reason for this, as some narrations state, is that one does not know where the blessing lies in the food. Therefore, the Prophet (may Allah's peace and blessings be upon him) ordered licking one's fingers, because the blessing may be in the traces of food on fingers.