How we cite our quotes: All quotations are from Harry Potter and the Deathly Hallows – Part 1.
Quote #7
HERMIONE: No, you don't understand. Dirt and rust have no effect on the blade. It only takes in that which makes it stronger.
Here, Hermione is talking about the sword of Gryffindor—which, miraculously, only drinks in stuff that makes it more powerful. She's realized that the sword can destroy Horcruxes because it imbibed basilisk venom back when Harry used it on—you guessed it—a basilisk in the Chamber of Secrets.