People telling many lies about a person is spoken of as if they made the person dirty by spreading lies over him. (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here "hearts" represents the people's wills. A person being stubborn is spoken of as if their hearts or wills were hard like a rock. AT: "They are stubborn" (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-metaphor]])