大般涅槃經義記 1.179

1.179

正應先明諸行無常，後類於佛，今此何故先說諸佛境界無常，後類諸行？釋言：取義左右不同。若欲知佛有為無常，舉行以類；若欲令人知行無常，舉佛以類。然今化意為使眾生因佛無常，知有為行無常可厭，故先舉佛，後類諸行。

Properly speaking, one should first explain the impermanence of all conditioned formations, and afterwards analogize to the Buddha; why does it here first speak of the impermanence of the realms of all buddhas, and afterwards analogize all conditioned formations? The explanation says: the meanings taken in either direction are different. If one wishes to know that the Buddha is conditioned and impermanent, one raises conditioned formations to analogize him; if one wishes to cause people to know that conditioned formations are impermanent, one raises the Buddha to analogize them. However, here the intention of transformation is to cause sentient beings, through the Buddha's impermanence, to know that conditioned formations are impermanent and should be reviled; therefore it first raises the Buddha, and afterwards analogizes all conditioned formations.