It is stated in the Discourse on the Diamond Scalpel by Grand Master Dengyō:
“The truth that motivates the bodhisattvas to take the Four Great Vows is the Four Noble Truths (the truth regarding the suffering, the cause of suffering, the extinction of suffering, and the path to enlightenment). Delusion of life and death that everything in the universe (3,000 Existences in the 100 Realms) repeats is the truth that life is full of suffering. Realizing in mind and body that this delusion of life and death is itself enlightenment is called the ‘vow to save all the people.’ The existence of three delusions in everything in the universe (delusion in view and thought, delusion that prevents bodhisattvas from mastering the teaching and saving the people, and delusion concealing the fundamental truth) is expressed as the ‘truth that the cause of suffering is evil passions.’ Realizing in mind and body that the evil passions themselves are enlightenment is called the ‘vow to eliminate evil passions however numerous they are.’ Extinction of suffering of life and death is called ‘the truth that extinguishes the evil passions.’ Since suffering of life and death is itself enlightenment, realizing the Buddha-nature of the perfect teaching is called the ‘vow to attain the supreme teaching of the Buddha.’ Delusion itself is enlightenment and at once the wisdom of the Buddha. Therefore, bodhisattvas take a vow to study all the teachings of the Buddha however limitless they are. As delusion and the wisdom of the Buddha are inseparable, people and the Buddha are one and the same. Both delusion regarding the suffering and cause of suffering and enlightenment by the extinction of suffering and the path to enlightenment exist in mind. The four great vows of bodhisattvas are fused in one’s mind and the one becomes all. This teaching of the Buddha is extremely important.”
Nizen Nijō Bosatsu Fu-sabutsu Ji, Never-Attaining Buddhahood by the Two Vehicles and Bodhisattvas in the Pre-Lotus Sūtras, Writings of Nichiren Shōnin, Doctrine 3, Page 221-222