首楞嚴義疏注經 3.548

3.548

舜若多，云空也。虛空之性不可銷滅，今尚可滅；上求下化菩提之心終無移動，故不動轉。爍迦羅，云竪固不壞也，又翻為輪。輪有摧碾，謂悲智之心自利利他，皆能摧碾惑業苦故。

Śūnyatā means emptiness. The nature of space cannot melt away, yet here it might even be extinguished; but this bodhicitta of seeking above and converting below will never shift, hence it is 'not moved or turned.' Cakra means solid and indestructible; it is also translated as 'wheel.' A wheel has the function of crushing, meaning that the mind of compassion and wisdom, benefiting oneself and benefiting others, can both crush afflictions, karmas, and sufferings.