大般涅槃經義記 6.196

6.196

第二如來就人重問，迦葉答佛明其不定，聖渡可思、凡渡不思。此明聖人能渡可思，喻明地上菩薩能渡是可思議。

Second, the Tathāgata asks again with reference to humans, and Kāśyapa replies to the Buddha, clarifying that it is not fixed: a noble person's crossing is conceivable; an ordinary person's crossing is inconceivable. This clarifies that a noble person's ability to cross is conceivable, which analogizes and clarifies that the ability of a bodhisattva on the bhūmis to cross is conceivable.