大乘起信論義記 3.426

3.426

言分別生滅相者，依生滅門觀察法相，故言分別。如《瑜伽論．菩薩地》云「此中菩薩即於諸法無所分別，當知名止。若於諸法勝義理趣，及諸無量安立理趣世俗妙慧，當知名觀。」是知依真如門止諸境相無所分別，即成根本無分別智；依生滅門分別說相，觀諸理趣，即成後得智。然二門唯一心故，是故雙運方得名為正止觀也。

As for 'discerning the marks of arising and ceasing': one examines dharmas based on the gate of arising and ceasing; hence it is called 'discerning.' As stated in the 'Bodhisattvabhūmi' of the Yogācārabhūmiśāstra: 'Here, that a bodhisattva is without discrimination regarding all dharmas should be known as calming. The mundane marvelous wisdom regarding the principles of ultimate truth and the principles of immeasurable conventional designation in all dharmas should be known as insight.' From this we know that relying on the gate of tathatā to put an end to all object-marks without discrimination accomplishes fundamental non-discriminative cognition; relying on the gate of arising and ceasing to discern phenomenal marks and observe all principles accomplishes subsequently attained cognition. Yet because the two gates are only the One Mind, operating both in tandem is truly entitled to be called correct calming and insight.