Nichiren Daishoinin states in "True Entity of Life,"
Exert yourself in the two ways of practice and study. Without practice and
study, there can be no Buddhism. Both practice and study arise from faith.
(Gosho, p. 668; MW-1, p. 95)
Practice and study originate in faith, and at the same time, exerting ourselves in practice and study is a natural consequence of believing. When these three arise in the life of the practitioner, the sense of joy becomes evident.