大般涅槃經義記 1.150

1.150

問曰：純陀難破無差，成佛無常，今言如來後受施時，法身、常身、無邊身等，已知佛常，何須更難？釋言：純陀道佛常者，一得不退故名為常，非是凝然，故得為難。亦可純陀且縱佛常令與昔差，今昔既差，還是無常，難意如是。

Question: Cunda refutes "no difference" to establish that the Buddha is impermanent; now by saying that when the Tathāgata subsequently received the giving he was the dharmakāya, a permanent body, a boundless body, and so forth, he already knew that the Buddha is permanent—why need he raise further objections? Explanation: What Cunda called the Buddha's permanence meant that once attained, he does not regress, which is therefore called permanence, not that he is statically unchanging; hence he could raise the objection. Alternatively, Cunda temporarily conceded the Buddha's permanence to make it differ from the past; since the present and the past differ, it is still impermanence—such was the intent of his objection.