大般涅槃經義記 6.203

6.203

下明出世菩薩不思亦有三種：一證菩提行、二益眾生行、三離有為行。初中「菩提不可喻比」所證深也。菩提真性離相無為，故不可比，如《維摩》說「寂滅是菩提，滅諸相故；不觀是菩提，離諸緣故；不行是菩提，無憶念故；無比是菩提，不可喻故」，如是等也。「心亦不可以喻比」者，證心寂滅，無相無緣，故不可比。「而可說」者，菩提及心雖不可比而得宣說。心證菩提故不可思，良以是心本從緣染，後息妄染，內照實性，所以可說。行證之時，法從心現，不從外來，故無師諮而能自得阿耨菩提。

Below, it clarifies that the supramundane bodhisattva being inconceivable also has three kinds: first, the practice of realizing bodhi; second, the practice of benefiting sentient beings; third, the practice of departing from the conditioned. In the first, "Bodhi cannot be compared by analogy" refers to the profundity of what is realized. The true nature of bodhi is free from marks and unconditioned, hence it cannot be compared, as the Vimalakīrti says: "Quiescence is bodhi, because it extinguishes all marks; non-contemplation is bodhi, because it is free from all conditions; non-action is bodhi, because it is devoid of recollection; incomparability is bodhi, because it cannot be analogized," and so forth. "The mind also cannot be compared by analogy" means that the realizing mind is quiescent, markless, and free from conditions, hence it cannot be compared. "Yet it can be spoken of" means that although bodhi and the mind cannot be compared, they can be expounded. The mind realizes bodhi and is therefore inconceivable; truly because this mind originally was defiled dependent on conditions, later it ceases delusional defilement and inwardly illuminates the true nature, and therefore it can be spoken of. At the time of experiential realization, the Dharma manifests from the mind and does not come from outside; hence without consulting a teacher, they can naturally attain anuttarā bodhi.