首楞嚴義疏注經 8.107

8.107

即寂之照，故曰心光。即照之寂，名佛常凝。此圓定慧離二邊染，斷性亦無，故云無上妙淨。二邊不動即無為作，故云安住無為也。得無遺失，戒圓明也。此則定道圓融，離妄想染，故云戒心。

Illumination being identical to quiescence is called the 'light of the mind.' Quiescence being identical to illumination is called 'the Buddha's constantly congealed.' This complete concentration and wisdom is free from the defilement of the two extremes, and even the nature of severing is absent; hence it says 'unsurpassed, wondrous purity.' Being unmoved by the two extremes is itself unconditioned activity; hence it says 'dwelling securely in the unconditioned.' Obtaining without loss refers to the precepts being completely clear. This, then, is the complete interfusion of concentration and path, free from the defilement of delusional thoughts; hence it is called the mind of precepts.