大般涅槃經義記 9.157

9.157

自下第二答上問中兩足妙藥。於中迦葉先問發起。前已問竟何勞更問？去問遠故。此問與前有何差別？前直讚問，讚佛所說法為妙藥。今於此處具為兩門：一讚、二難，初至「亦知未來諸根」是其讚問，「如是眾生於佛滅」下是其難問。迦葉前者何不即難，至此方為？前者若舉二十一對諍論難佛，言辭浮廣不成偈義，為是不難。由前不難，故此為之。今此何不望直為難，先為讚乎？將奪先與，為難法爾，故先嘆之。嘆中，「如來具足根力」牒佛前言，下明所知。所知有三：一知眾生上中下根、二知諸根利鈍差別、三知眾生現未根別。

From here down, the second part answers [the question on] the wondrous medicine for the two-footed among the questions above. Within this, Kāśyapa first initiates it by asking a question. Since he had already asked previously, why take the trouble to ask again? Because the previous question was far away. What difference is there between this question and the earlier one? The earlier one simply praised and questioned, praising the Dharma spoken by the Buddha as a wondrous medicine. Now in this place, it comprises two approaches: first, praise; second, challenge. From the beginning up to "and also knows the future faculties" is his praising question; from "Such sentient beings, after the Buddha's parinirvāṇa..." downward is his challenging question. Why did Kāśyapa not raise the challenge right away earlier, and only do so now? If earlier he had adduced the twenty-one pairs of disputations to challenge the Buddha, the wording would have been vast and diffuse and would not have formed the meaning of verses; therefore he did not challenge then. Because he did not challenge earlier, he does so here. Why here does he not directly challenge, but first praise? When about to take away, one first gives; this is the normal method of raising a challenge, so he first praises. Within the praise, "The Tathāgata is fully endowed with the power of the faculties" cites the Buddha's earlier words; below he clarifies what is known. What is known has three parts: first, knowing sentient beings' superior, middling, and inferior faculties; second, knowing the distinction between sharp and dull faculties; third, knowing the distinction between sentient beings' present and future faculties.