仁王護國般若波羅蜜多經疏 3.246

3.246

解行名者，觀法實相照理現前，名善現行，擇法為性也。無相甚深者，如經說云「念念觀察一切眾生無性為性，一切諸法無為為性，一切國土無相為性。」即相觀性，名為甚深。修慧行也。從此第七明無著行。

Explaining the name of the practice: Contemplating the true mark of dharmas and illuminating principle so that it manifests before one is called the practice of skillful manifestation; investigation of dharmas (dharmapravicaya) is its nature. "Signlessness is profound": as the sūtra says: "Thought after thought observing that all sentient beings have no-nature as their nature, all dharmas have the unconditioned as their nature, and all lands have signlessness as their nature." Contemplating nature through signs is called profound. This is the practice of cultivating wisdom. From here, the seventh clarifies the practice of non-attachment.