金剛般若經依天親菩薩論贊略釋秦本義記卷上 1.34

1.34

經。須菩提於意云何東方虛空可思量不　第四喻也。喻中有二。一略舉東方。二廣引九方。就初喻中文復有二。一如來問。二善現問答。此即問也。虛空界非十方。方是不相應行法色上假立。今以方辨空故。名東方虛空耳。

[Sūtra:] "Subhūti, what do you think? Can the space of the eastern direction be measured?" The fourth section is the simile. In the simile there are two parts: first, briefly mentioning the eastern direction; second, broadly citing the nine directions. In the first simile there are again two parts: first, the Tathāgata's question; second, Subhūti's response to the question. This is the question. The realm of space does not have ten directions; directions are dharmas non-concurrent with mind, nominally established upon physical form. Here, because space is distinguished by direction, it is merely called "the space of the eastern direction".