What an inspirational speaker said

An inspirational speaker said:
The best days of my life were the days I spent with another man's wife.
Audience were in shock and silence.
He added : "She was my mother".
A big round of applause and laughter followed.

An adventurous man tried to crack this at home. After dinner he told his wife:
The best days of my life were the days I spent with another man's wife.
After a moment he tried to recall the second line.
By the time he regained his senses, he was on a hospital bed, recovering from burns of boiling water.