Sahih al-Bukhari, Volume 7, Book 65, Hadith 366 (USC-MSA) ⓘ
Narrated Ibn `Abbas: The Prophet said, 'When you eat, do not wipe your hands till you have licked it, or had it licked by somebody else."
حَدَّثَنَا عَلِيُّ بْنُ عَبْدِ اللَّهِ، حَدَّثَنَا سُفْيَانُ، عَنْ عَمْرِو بْنِ دِينَارٍ، عَنْ عَطَاءٍ، عَنِ ابْنِ عَبَّاسٍ، أَنَّ النَّبِيَّ صلى الله عليه وسلم قَالَ " إِذَا أَكَلَ أَحَدُكُمْ فَلاَ يَمْسَحْ يَدَهُ حَتَّى يَلْعَقَهَا أَوْ يُلْعِقَهَا " .
also referenced under: Book 70, Hadith 85 (In-Book) & Hadith 5456 (DarusSalam)