It is preached in the “Medicine King Bodhisattva” chapter of the Lotus Sūtra, fascicle 7: “Suppose there is a man who donates the seven treasures overflowing the triple thousand worlds to the Buddhas, great bodhisattvas, Pratyekabuddha and arhats. The merit of this man, though great as it is, cannot match to the great merit of upholding a stanza or a verse of the Lotus Sūtra.” Grand Master T’ien-t’ai interprets this in his Words and Phrases of the Lotus Sūtra, fascicle 10: “The reason why upholding a verse of the Lotus Sūtra is more meritorious than donating the seven treasures to the four holy ones is that the Dharma, even in verse form, is the teacher of the holy ones.”

Hōkyō Hōjū Ji, The Dharma Is More Precious Than Treasures, Wooden Statues or Portraits, Writings of Nichiren Shōnin, Faith and Practice, Volume 4, Page 94-95