Prophet Muhammad (pbuh) was once eating with a group of
young children.
Suddenly he smiled. The children asked him why he was
smiling. Prophet Muhammad (pbuh) replied:
“Shaytan has just vomited”
He then explained that there was a child amongst them who
had forgotten to say Bismillahirrahmaanirraheem (I begin in
the name of Allah, the Kind, the Merciful) and Shaytan had sat
to eat with him.
The child had just remembered and said:
Bismillahirrahmaanirraheem
With the name of Allah, from the beginning to the end.
Shaytan therefore vomited and thus the Prophet (pbuh) had
smiled.
Excellent Stories Vol 1