The doctrine of obtaining Buddhahood by the Two Vehicles is not expounded in sūtras of the first four of the Five Flavors, such pre-Lotus sūtras as the Flower Garland Sūtra, Āgama sūtras, Hōdō sūtras (various Mahāyāna sūtras), and the Wisdom Sūtra. Since various pre-Lotus sūtras do not preach the attainment of Buddhahood by the Two Vehicles, the attainment of Buddhahood by bodhisattvas is impossible through the Four Teachings expounded in those sūtras. Bodhisattvas say in the Flower Garland Sūtra that their vow will never be completed until all people attain Buddhahood. All bodhisattvas invariably take four great vows. When the first vow “to save all the people” is not fulfilled, the last vow “to attain the supreme teaching of the Buddha” will not be completed. In this respect, the bodhisattvas’ vow is not completed by the pre-Lotus sūtras preached during the first forty years or so which do not expound the attainment of Buddhahood by the Vehicles.

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 219-220