Full of Light Prophet Mohammed, may Peace of Allah Almighty be upon him, used to smile, and that too a lot. Laughing is discouraged. When a Friend of Allah laughs then it has a completely diffent meaning. When a hot plate becomes very hot we see drops of fire on it. We say that the hot plate is laughing. The laughing of people of Allah has the similar connotation. If you touch a laughing hot plate you'll get a nasty burn.
(Sitting (majlis) on Sunday, August 22, 2010)