This letter was written at Minobu in the eighth month of the first year of Kenji (1275) to the lay nun Myōshin, a believer who lived in Nishiyama in Fuji District of Suruga Province. It explains that the Gohonzon is “the essence of the Lotus Sutra and the eye of all the scriptures.” The Gohonzon, or mandala, embodies the reality of the three thousand realms in a single moment of life implicit in the “Life Span” chapter of the Lotus Sutra. Thus, the Gohonzon is the “essence of the Lotus Sutra.” And the Lotus Sutra is the eye of all the teachings of Shakyamuni. Therefore, the Gohonzon, the “essence of the Lotus Sutra,” is also the “eye of all the scriptures.”

https://www.nichirenlibrary.org/en/wnd-1/Content/73