俱舍論記 22.57

22.57

「由性非常至一如苦受」者，論主答。由性非常，簡異滅諦；違聖心故，簡異道諦，故名為苦。如以行苦相觀色等時，非彼行苦相一如苦受，顯苦受差別。

Regarding "Because its nature is impermanent... exactly like painful feeling": the author of the treatise answers. Because its nature is impermanent, it is distinguished from the truth of cessation; because it opposes the noble mind, it is distinguished from the truth of the path; therefore it is called suffering. Just as when one contemplates form and the rest with the aspect of the suffering of conditioned existence, that aspect of the suffering of conditioned existence is not entirely identical with painful feeling, showing the distinction of painful feeling.