The comparative superiority of all the sūtras preached during fifty years or so by Śākyamuni Buddha is declared in chapter 10 of the Lotus Sūtra, “The Teacher of the Dharma”: “I have expounded numerous sūtras. I am now expounding this sūtra. I also will expound many sūtras in the future. The total number of the sūtras will amount to many thousands, ten thousands and millions of them. This Sūtra of the Lotus Flower of the Wonderful Dharma is the most difficult to believe and the most difficult to understand.”
Even if this statement of the Lotus Sūtra were uttered by Śākyamuni Buddha alone, anybody from the highest ranking bodhisattvas down should respect and believe in it. The Buddha of Many Treasures, coming from the Eastern Hōjō World, attested to its truth. Besides, various Buddhas in manifestation from all the worlds in the universe gathered to verify its truth “with their long and wide tongues extended to the Brahma Heaven” just as Śākyamuni Buddha did, and returned to their respective lands.
The three phrases of “already preached, being now preached, and going to be preached” (i, kon, tō) include all the sūtras preached not only by Śākyamuni Buddha during fifty years or so of His preaching but also by all the Buddhas from all the worlds in the universe through the past, present, and future. These numerous sūtras are all compared with the Lotus Sūtra. Suppose that these Buddhas, from all the worlds in the universe, who presented themselves at the assembly of the Lotus Sūtra and added their seals of approval, should return to their respective homelands and say to their disciples that there is a sūtra superior to the Lotus Sūtra, would their disciples trust them at all?
Hōon-jō, Essay on Gratitude, Writings of Nichiren Shōnin, Doctrine 3, Pages 5.