It is recommended to lick one's fingers and wipe the bowl, and to eat a piece of food that is dropped after removing any dirt on it. It is disliked to wipe one's hand before licking it, because of the possibility that the blessing of the food may be in that remaining part. The Sunnah is to eat with three fingers Sahih Muslim 2033 a
Arabic hadith text
وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا سُفْيَانُ بْنُ عُيَيْنَةَ، عَنْ أَبِي الزُّبَيْرِ، عَنْ جَابِرٍ،
أَنَّ النَّبِيَّ صلى الله عليه وسلم أَمَرَبِلَعْقِ الأَصَابِعِ وَالصَّحْفَةِ وَقَالَ " إِنَّكُمْ لاَ تَدْرُونَ فِي
أَيِّهِ الْبَرَكَةُ "
Translation
Jabir reported that Allah's Messenger (ﷺ) commanded the licking of fingers and the dish, saying
You do not know in what portion the blessing lies."