WHAT TO DO IF YOU FORGET TO SAY 'BISMILLAH' H 736 "When you begin to eat you should pronounce the Name of Allah, the Exalted. If you forget to do it in the beginning, you should say, 'In the Name of Allah, in its beginning and at its end.'" R 736 Abu Daud Tirmidhi with a chain up to the Mother of Believers, Lady Ayesha, may Allah be pleased with her, related that the Prophet, praise and peace be upon him, said this.
728- وعن عائشة رضي الله عنها ، قالت : قَالَ رسول الله صلى الله عليه وآله وسلم : "إِذَا أكَلَ أحَدُكُمْ فَلْيَذْكُرِ اسْمَ اللهِ تَعَالَى، فإنْ نَسِيَ أنْ يَذْكُرَ اسْمَ اللهِ تَعَالَى في أوَّلِهِ، فَلْيَقُلْ: بسم اللهِ أوَّلَهُ وَآخِرَهُ" رواه أَبُو داود والترمذي، وقال: "حديث حسن صحيح" .