大方廣圓覺修多羅了義經略疏 2.1257

2.1257

知眾生念者，世界既全成覺，眾生全在覺中，故所起念無不了達，如影入鏡鏡照無遺。

Regarding knowing the thoughts of sentient beings: since the world has fully become enlightenment, and sentient beings are entirely within enlightenment, whatever thoughts they give rise to are thoroughly understood without exception, just as when a shadow enters a mirror, the mirror illuminates it without leaving anything out.