首楞嚴義疏注經 9.204

9.204

正顯未盡色陰也。心入正定，如明目人。未破色陰，如大幽暗。精性妙淨，定心顯也，心未發光，慧未生也。區宇，寰區，此如王所統有諸國土，故云區。區，別也。皆一天所覆，故云宇。宇，猶覆也。今色陰二字即同區宇，同一陰覆色等別故。舉此喻者，表在其中也。

This directly reveals the unexhausted aggregate of form. The mind entering right concentration is like a person with clear eyes. Not yet breaking the aggregate of form is like vast, dense darkness. 'The refined nature is wondrously pure' reveals the concentration mind; 'the mind has not yet emitted light' means wisdom has not yet arisen. 'Realm' (區宇) refers to an expanse of territory: this is like the various lands ruled by a king, hence called *qū* (區); *qū* means distinct division. All are covered by the one sky, hence called *yǔ* (宇); *yǔ* means canopy. Here, the two words 'aggregate of form' are identical to 'realm', because they are covered by the same aggregate while form and the rest are distinct. Bringing up this metaphor indicates being within it.