首楞嚴義疏注經 10.223

10.223

此明中虛實非所歸而計於歸，故云歸無歸執。無想天五百大劫想心不行也。舜若多，四空處也。圓虛無心，斷滅因也。空亡果，斷滅果也。

This voidness within the clarity is not truly a refuge, yet they take it as a refuge; hence it is called 'the attachment to taking refuge where there is no refuge.' In the heaven of no thought, for five hundred great kalpas, the thinking mind does not function. 'Śūnyatās' refers to the four formless realms. 'Perfect voidness without mind' is the cause of utter extinction. 'The fruit of empty annihilation' is the fruit of utter extinction.