大般涅槃經集解 5.32

5.32

案道生曰：以佛所說為證，真實之理本不變也。唯從說者得悟，乃知之耳。所說之理既不可變，明知其悟亦湛然常存也。僧亮曰：諸佛所師，涅槃法也。若佛無常，法亦無常，故云所說真法亦無信者。慧朗別述曰：第四譬也。彼之家人所以不復愛是子者，緣有可信相師妄想說也。若人聞汝謂佛無常，汝是可信之人，亦可緣汝而不信也。

Daosheng states: Taking what the Buddha taught as proof, the real principle is fundamentally unalterable. It is only known when one attains awakening through the teacher. Since the principle taught cannot alter, one clearly knows that awakening to it also serenely endures permanently.
Sengliang states: What all Buddhas take as their teacher is the dharma of nirvāṇa. If the Buddha were impermanent, the Dharma would also be impermanent; hence it is said that no one would believe the true Dharma he taught either.
Huilang's distinct commentary states: This is the fourth parable. The reason the family members no longer loved this child was due to the deluded pronouncement of a trustworthy physiognomist. If people hear you say the Buddha is impermanent, since you are a trustworthy person, they might also not believe on your account.