大毘盧遮那成佛經疏 2.72

2.72

第四十三「云何水心？謂順修洗濯一切不善法」者，如水性清潔，雖暫為諸垢所污，澄之則淨，又能洗除垢穢。此人心亦爾，常欲發露垢惡，懺洗三業眾罪。以見此垢此淨，我如是行，則能障礙淨心。但當觀心實相，了從本來垢法不生，自能除一切蓋障，是彼治行也。

The forty-third: "What is the water mind? It is following the practice of washing away all unwholesome teachings." Just as the nature of water is pure—even if temporarily defiled by stains, it becomes clear when settled, and it can also wash away dirt and filth; this person's mind is also like this: it constantly wishes to disclose defilements and evil, confessing and washing away the manifold sins of the three karmas. Because of seeing "this is defiled" and "this is pure," and "I practice in this way," this can obstruct the pure mind. One should simply contemplate the dharmatā of the mind and realize that from the beginning defiled phenomena are unborn, which will naturally eliminate all hindrance-coverings; this is its counteracting practice.