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 رَسُولَ اللهِ ﷺ كَانَ إِذَا أَكَلَ طَعَامًا لَعِقَ أَصَابِعَهُ الثَّلَاثَ وَقَالَ إِذَا مَا وَقَعَتْ لُقْمَةُ أَحَدِكُمْ فَلْيُمِطْ عَنْهَا الْأَذَى وَلْيَأْكُلْهَا وَلَا يَدَعْهَا لِلشَّيْطَانِ وَأَمَرَنَا أَنْ نَسْلِتَ الصَّحْفَةَ وَقَالَ إِنَّكُمْ لَا تَدْرُونَ فِي أَيِّ طَعَامِكُمُ الْبَرَكَةَ