In the book of The Wonderful Story of Henry Sugar by Roald Dahl, Henry Sugar was a rich man, whose wealth was inherited from his dad. He never worked, nor did his wealthy friends.
There is a piece of description about Henry Sugar's character:
Henry had never done a day's work in his life, and his personal motto, which he had invented himself, was this: It is better to incur a mild rebuke than to perform an onerous task. His friends thought this was hilarious.
"Rebuke" means to tell off somebody. "Mild" means not so harsh. "To perform an onerous task" means to do honest and hard work, to earn money.
Why did the author suddenly mention that Henry might incur some mild rebukes? Does it imply that the way he spent his money has incurred some rebukes from the working class? If yes, why does this motto sounded very funny to his equally wealthy friends?