Nichiren on why correct doctrine is important with commentary

“Fifth, there is the threefold contemplation in a single mind that concerns doctrines. One hears the various doctrines such as those pertaining to the five periods and the eight teachings, and after storing these doctrines in the mind, one carries out meditative practice. Therefore it is called the threefold contemplation ‘that concerns doctrines.’"

Likewise, storing such doctrines as the identity and real reality of the Eternal Buddha Shakyamuni, the general and the specific, and the supremacy of the Lotus Sutra, for example, one carries out the chanting Namu Myoho renge kyo. 

However, there is little benefit in storing such erroneous and fabricated doctrines as SGI Ikeda-disciple amd NST High Priest.