法華玄義釋籤 9.7

9.7

凡譬喻法，或以實事、或以假設。如佛說言：若令樹木解我語者，我亦說令得須陀洹。但樹木無解語者，佛為解語人引此喻耳。又須菩提欲引般若之力大故，故云設有法過涅槃者，以智慧力亦能破之，故云如幻。

In general, the method of parables employs either real facts or hypothetical assumptions. Just as the Buddha said: 'If trees could understand my words, I would also cause them to attain stream-entry.' Yet trees have no capacity to understand words; the Buddha merely drew this parable for people who understand words. Furthermore, because Subhūti wished to show the greatness of the power of prajñā, he said that even if there were a dharma surpassing nirvāṇa, the power of wisdom could also dismantle it; hence he said it is like an illusion.