There are two kinds of people who harm the Lotus Sūtra. The first kind are those in whom the seed of Buddhahood was planted in a past life. The seed germinated and grew in them while they aspired for enlightenment, and they are close to attaining Buddhahood in this existence. For those in this category, should they slander the practicer of the Lotus Sūtra, their mouths would be shut and their heads split into pieces. The second kind of people are those who slandered the practicer of the Lotus Sūtra in previous lives as well as in the present life. Such people are being tormented in the Hell of Incessant Suffering life after life and their mouths are not sealed no matter how much they slander. For instance, a felon in prison waiting to be executed will not receive additional punishment till his execution, no matter how many evil acts he commits in prison. On the other hand, a prisoner who is scheduled to be released will be immediately punished should he commit an evil act in prison.

Hōren-shō, Letter to Hōren, Writings of Nichiren Shōnin, Volume 6, Followers I, Page 62