大般涅槃經義記 4.63

4.63

上來廣明佛性難見，下明二乘依經能見。迦葉先請「佛性微細，云何肉眼而能得見」，下佛答之，先明二乘依經信見，「如是佛性唯佛知」下彰彼二乘不能證見。前中先喻，次合顯法，「是故」已下結勸學經。

The above has extensively explained that the buddha-nature is difficult to see; below, it explains that the two vehicles are able to see it by relying on the sūtra. Kāśyapa first asks: 'The buddha-nature is subtle and fine; how can the flesh eye be able to see it?' Below, the Buddha answers him: he first explains that the two vehicles see through faith by relying on the sūtra; from 'such buddha-nature is known only by the Buddha' onward, he makes clear that those of the two vehicles cannot realize and see it. In the former part, there is first an analogy, next an application to reveal the Dharma; from 'therefore' onward, it concludes by exhorting the study of the sūtra.