Hilaire Belloc's "Matilda" is a retelling of an ancient story that appears in Aesop's Fables about "the boy who cried wolf." The moral of the story is that those who gain a reputation for lying will not be believed even when they are telling the truth.
The themes of disobedience and punishment are closely linked in "Matilda" because the punishment derives directly and logically from the disobedience. Fate can deal out punishments that would seem horrifyingly cruel if they were the result of human agency. Imagine a slight change in the story of this poem. Matilda told terrible lies, and one day she pretended that her house was burning down. She summoned the fire brigade, causing considerable inconvenience to everyone. Her aunt, exasperated by Matilda's behavior, therefore punished her by burning her to death.
This version of the story would make the reader feel that Matilda's punishment was intolerably harsh and that her aunt was a monster. However, as the narrative stands, no one wants to kill Matilda as a punishment for her lies. They merely do not believe that she is in any danger. The punishment, therefore, fits the crime, not in terms of severity, but because it is the direct result of Matilda's transgression. Belloc therefore suggests that lying is not only morally wrong, but stupid and dangerous, making a causal link between the virtue of honesty and self-preservation.