What is one way that Longfellow uses source material from the story of Sampson in "The Warning"? Longfellow shares Sampson’s story of revenge to develop the theme that those who use force to deny others their freedom will eventually fail. He includes details about Sampson’s attention to his hair to convey the idea that vanity can be a source of weakness. Longfellow draws from Sampson’s betrayal by his love to emphasize the potential danger in trusting others. He uses the example of Sampson’s imprisonment to demonstrate the consequences of rebelling against those in authority.