金剛般若經依天親菩薩論贊略釋秦本義記卷上 1.34

1.34

[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".