Excellence of Eating with Three Fingers and Licking Them Riyad as-Salihin 749
Arabic hadith text
وعن جابر رضى الله عنه أن رسول الله صلى الله عليه وسلم أمر بلعق الأصابع والصحفة، وقال: "إنكم لا تدرون في أي طعامكم البركة".((رواه مسلم))
Translation
Jabir (May Allah be pleased with him) reported
The Messenger of Allah (ﷺ) commanded the licking of fingers and the gleaning of the dish, saying, "You do not know in which portion the blessing lies."[Muslim].