Jabir reported Allah's Messenger (ﷺ) as saying: When any one of you drops a mouthful he should pick it up and remove any of the filth on it, and then eat it, and should not leave it for the Satan, and should not wipe his hand with towel until he has licked his fingers, for he does not know in what portion of the food the blessing lies.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ نُمَيْرٍ، حَدَّثَنَا أَبِي، حَدَّثَنَا سُفْيَانُ، عَنْ أَبِي الزُّبَيْرِ، عَنْ جَابِرٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِذَا وَقَعَتْ لُقْمَةُ أَحَدِكُمْ فَلْيَأْخُذْهَا فَلْيُمِطْ مَا كَانَ بِهَا مِنْ أَذًى وَلْيَأْكُلْهَا وَلاَ يَدَعْهَا لِلشَّيْطَانِ وَلاَ يَمْسَحْ يَدَهُ بِالْمِنْدِيلِ حَتَّى يَلْعَقَ أَصَابِعَهُ فَإِنَّهُ لاَ يَدْرِي فِي أَىِّ طَعَامِهِ الْبَرَكَةُ " .
sunnah.com