When any one of you drops a mouthful he should remove anything filthy from it and then eat it, and should not leave it for the Satan. He also commanded us that we should wipe the dish saying: You do not know in what portion of your food the blessing lies. (Using translation from Muslim 2034)
أَنَّ النَّبِيَّ ﷺ كَانَ يَلْعَقُ أَصَابِعَهُ الثَّلَاثَ إِذَا أَكَلَ وَقَالَ إِذَا وَقَعَتْ لُقْمَةُ أَحَدِكُمْ فَلْيُمِطْ عَنْهَا الْأَذَى وَلْيَأْكُلْهَا وَلَا يَدَعْهَا لِلشَّيْطَانِ وَلْيَسْلُتْ أَحَدُكُمُ الصَّحْفَةَ فَإِنَّكُمْ لَا تَدْرُونَ فِي أَيِّ طَعَامِكُمُ الْبَرَكَةَ