عَنْ عَائِشَةَ رَضِيَ اللَّهُ عَنْهَا أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ كَانَ يَأْكُلُ طَعَامًا فِي سِتَّةِ نَفَرٍ مِنْ أَصْحَابِهِ فَجَاءَ أَعْرَابِيٌّ فَأَكَلَهُ بِلُقْمَتَيْنِ فَقَالَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ أَمَا إِنَّهُ لَوْ كَانَ ذَكَرَ اسْمَ اللَّهِ لَكَفَاكُمْ فَإِذَا أَكَلَ أَحَدُكُمْ طَعَامًا فَلْيَذْكُرِ اسْمَ اللَّهِ فَإِنْ نَسِيَ أَنْ يَذْكُرَ اسْمَ اللَّهِ فِي أَوَّلِهِ فَلْيَقُلْ بِسْمِ اللَّهِ أَوَّلَهُ وَآخِرَهُ
Lady Aisha (may Allah be pleased with her) narrates that the Noble Prophet (peace and blessings be upon him) was eating food with six of his companions when a Bedouin came and finished the food in two bites. The Noble Prophet (peace and blessings be upon him) said: If he had recited Bismillah before eating, this food would have sufficed for all of you. When any of you eats food, he should recite Bismillah, and if he forgets to recite Bismillah at the beginning, he should say: Bismillahi awwalahu wa akhirahu.