首楞嚴義疏注經 6.265

6.265

虛空藏菩薩由觀四大無依，妄想生滅，虛空無二、佛國本同，得無生忍。今謂虛空昏暗，無明所生，非是覺明，異于本覺，故須揀也。

Bodhisattva Ākāśagarbha, by contemplating that the four great elements have no support, false thoughts arise and cease, space is non-dual, and buddha-realms are fundamentally identical, attained the forbearance of non-arising dharmas. Here it means: empty space is dark and dull, born of ignorance; it is not the luminousness of awareness and differs from original awakening; therefore it must be selected out.