大乘起信論裂網疏 6.98

6.98

此先明苦諦觀也。一生滅不停是無常行，無常故苦即是苦行，苦故無我。過去如夢了不可得，現在如電剎那不住，未來如雲忽起無所從來，即無我行。諸蟲穢污等即不淨行。此四行觀，對治凡外一切見愛無不盡也。

This first clarifies the contemplation of the truth of suffering. Arising and ceasing without ceasing is the practice of impermanence. Because of impermanence, there is suffering, which is the practice of suffering. Because of suffering, there is non-self. The past is like a dream, utterly unobtainable; the present is like lightning, not abiding for an instant; the future is like clouds, suddenly arising with nowhere from which they come—this is the practice of non-self. Foul with various worms and so forth is the practice of impurity. These four aspects of contemplation counteract all views and cravings of ordinary beings and outsiders without exception.