大般涅槃經義記 2.201

2.201

上來明佛法身體常，自下第二拂去迹疑，化跡濫真故須拂遣。於中初先拂去形迹；二「迦葉復言：如來云何名常住」下拂去言迹。拂形迹中，迦葉先問「如佛言曰我已久渡煩惱大海」，牒佛前言，名前出於無量煩惱為久渡也。「若佛」已下執迹為難。若佛已渡，何緣復共邪輪陀羅舉實徵迹？以是因緣，當知未渡，執迹疑實。「唯願」已下請佛釋通。下佛答之，先呵難辭，「能建」下釋。釋意如何？明昔納妃生子之事，是大涅槃所起德用，非實煩惱。釋相如何？汎舉涅槃所起德用類以釋之。「大般涅槃能建大義」，總舉類答。義猶用也，建猶起也，大般涅槃能起大用，用相非一，名建大義。

The above clarifies that the Buddha's dharmakāya is permanent in its substance; from here down is the second part, brushing away doubts about traces—because the traces of transformation might be confused with the real, they must be brushed away. Therein, first he brushes away bodily traces; second, from 'Kāśyapa further said: How is the Tathāgata called permanently abiding?' onward, he brushes away verbal traces. In brushing away bodily traces, Kāśyapa first asks, 'As the Buddha said: I have long crossed the great ocean of afflictions'—repeating the Buddha's earlier words, designating the previous emergence from innumerable afflictions as having long crossed over. From 'if the Buddha...' onward, he grasps the traces to raise an objection: If the Buddha had already crossed over, for what reason did he take Yasodharā? He cites the actual to challenge the trace: from these causes and conditions, one should know he had not yet crossed over, grasping the traces to doubt the real. From 'I only wish...' onward, he requests the Buddha to explain and resolve it. Below, the Buddha answers him: first he rebukes the words of the objection, and from 'able to establish...' onward, he explains. What is the intention of the explanation? It clarifies that the past matters of taking a consort and fathering a child were the virtuous functions arising from great nirvāṇa, not real afflictions. What are the characteristics of the explanation? He generally cites the virtuous functions arising from nirvāṇa and assimilates them to explain it. 'Mahāparinirvāṇa is able to establish great purposes' generally cites the category in reply. 'Purpose' is like function; 'establish' is like arise: great nirvāṇa is able to give rise to great functions, and because the characteristics of these functions are not single, it is called establishing great purposes.