He said: "The best years of my life were spent in the arms of a woman who wasn't my wife!"
The audience was into silence and shock.
Imam Omar added: "And that woman was ... my Mother!"
There was laughter and applause from the audience.
Mouaniss, who was in training to become an Imam himself, had heard how effective the joke had been on the audience and planned to repeat it at his own Mosque the following week.
But he decided he needed to rehearse the lines at home first.
He walked into the kitchen and said loudly to his wife who was preparing dinner, "The greatest years of my life were spent in the arms of a woman who was not my wife!"
The wife went; "Ah!" with shock and rage.
Standing there for 20 seconds trying to recall the second half of the joke, Mouaniss finally blurted out, "... and I can't remember who she was!"
By the time Mouaniss regained his consciousness, he was on a hospital bed nursing burns from boiling water.
The post script to the story is that on hearing of the strife that Mouaniss had brought on himself over his joke Imam Omar issued this warning to his own congregation: "Never copy and paste in great haste!"