بِسْمِ اللَّهِ وَعَلَى بَرَكَةِ اللَّهِ
In the name of Allah and with the blessings of Allah I begin (eating)".
On forgetting to recite Bismillah at the beginning,
بِسْمِ اللَّهِ أَوَّلِهِ وَآخِرِهِ
"In the name of Allah in the beginning and end".
By not reciting Bismillah, Satan has an opportunity of partake in the food.