大般涅槃經義記 4.78

4.78

「從此」已下答上云何解滿字等，解經由字，是以辨之。於中有四：第一如來略言起發、二「迦葉白」下問答廣辨、三迦葉領解、四如來述嘆。初中，如來何因說言「種種異論皆是佛說」？因前說我從菩薩聞，故類一切皆是佛說。如來何意作如是語？欲使眾生習學文字以知經法，故發此言。

From "From this..." downward answers the earlier [question] of how to understand the complete letters, etc.; understanding the sūtras relies on letters, which is why they are explained. Therein there are four parts: first, the Tathāgata's brief statement initiates it; second, from "Kāśyapa said..." downward, questions and answers broadly distinguish it; third, Kāśyapa grasps and understands it; fourth, the Tathāgata praises it. In the first part, why does the Tathāgata say, "All the various diverse treatises are taught by the Buddha"? Because of the earlier statement that the self was heard from the bodhisattva, by analogy all are taught by the Buddha. With what intention did the Tathāgata make such a statement? Wishing to make sentient beings study the letters so as to know the sūtra teachings, he therefore uttered these words.