In "Don Quixote," the character reflects on the futility of kindness towards those who are inherently malicious. The saying suggests that acts of goodwill towards villains are ultimately wasted efforts, much like pouring water into the sea, where it disappears without trace or effect. This insight reveals a deep understanding of human nature and the challenges in dealing with unscrupulous individuals.

Through this observation, Cervantes emphasizes the idea that some people are simply unworthy of goodwill. Rather than generating positive outcomes, kindness in such cases can be counterproductive. The quote serves as a reminder that discernment in choosing whom to help is essential, as not all actions towards others yield beneficial results.