Animals that lack human intelligence rely on physical tools to guide their movements. In much the same way, when a person abandons reason in favor of foolishness, physical restraint often becomes necessary. Tools from the world of animal training illustrate this reality: a whip is used to strike and guide, while a bridle or iron bit is designed to pull and lead a beast. Similarly, a rod is meant to strike the body of a foolish person.
The primary approach among commentators is that a direct parallel exists between animals and the fool. Humans are uniquely gifted with intellect and the free will to choose a good path. However, a foolish person surrenders to his desires and strays from wisdom. By doing so, he loses his human advantage and becomes like an animal driven purely by instinct. Because he is unable to absorb moral instruction or change his ways through words and logical explanations alone, the only method to correct him is through physical pain and strikes. This forces him to abandon his harmful behavior and return to a proper life [רלב״ג, מלבי״ם, מצודת דוד, עמנואל הרומי]. These punishments and painful experiences are prepared in advance, serving as the fitting consequence for the wicked and the foolish [רש״י, אבן עזרא].
Within this comparison to animals, there are different levels of a lack of understanding. A horse simply needs a whip to help guide its direction. A donkey, however, is considered more foolish, making a whip insufficient. It requires a bridle to physically stop it and prevent it from wandering off the path [מלבי״ם].
On the other hand, a different perspective highlights the complex nature of punishment, suggesting that using physical force against a fool might actually be useless. According to this view, striking will not always correct a foolish person, and his reaction can be as destructive as that of a startled animal. Some react like a horse struck by a whip—they break into a fast, uncontrollable run, plunging deeper into their foolishness where they cannot be stopped. Others react like a donkey being pulled by a bridle against its will. Angered by the blows, they become stubborn, harden their hearts, and firmly refuse to step away from their foolish behavior [אלשיך].