法苑珠林 99.70

99.70

又五百問事云。不得口吹經上塵。像塵准之。雖非正經然須慎之。亦不得燒故經。得重罪如燒父母。不知有罪者輕。

Furthermore, the Five Hundred Questions states: One must not blow off dust from sūtras with one's mouth; the dust on images is treated likewise. Even if it is not a genuine canonical text, one must still be cautious with it. Nor must one burn old sūtras; doing so incurs a grave sin like burning one's parents. For those who do not know it is a sin, it is lighter.