When the “Expedients” chapter of the Lotus Sūtra was preached, 5,000 self-conceited ones did not believe in what they heard and withdrew from the preaching of the Lotus Sūtra. Nevertheless, they became Buddhas in three months’ time because they did not slander the Lotus Sūtra. Referring to this incident, it is preached in the Nirvana Sūtra, “Both believers and non-believers will be born in the Immovable Land.” Those who heard the Lotus Sūtra can become Buddhas even if they do not put faith in the sūtra, so long as they do not slander it, due to the inexplicable merit of having heard the sūtra. This is like the person bitten by a poisonous snake called shichibuja who is bound to fall within taking seven steps and is unable to take the eighth step due to the inexplicable work of the poison. Or it is also like an embryo that changes its shape within seven days and never stays in one shape for more than eight days.

Hōren-shō, Letter to Hōren, Writings of Nichiren Shōnin, Volume 6, Followers I, Page 52