大般涅槃經集解 41.54

41.54

案僧亮曰：明此國土穢惡，眾生喜忘，故具有三種經也。智秀曰：第四正答所問也。明迦葉佛法理常不滅，正以學者根利，不須言說。由言教不興，故言滅也。

Sengliang comments: This clarifies that this land is foul and evil, and sentient beings are prone to forgetting; therefore it possesses all three kinds of sūtras.
Zhixiu comments: The fourth section directly answers what was asked. It clarifies that the principle of the Dharma of Krakucchanda Buddha is permanently unperishing; it was merely because practitioners had sharp faculties that words were not needed. Because the verbal teaching did not flourish, it is said to have perished.