大乘起信論裂網疏 4.95

4.95

眾生無始已來從未悟故，真如舉體而成生滅。捨生滅心，何處更有真如可觀？故須即從心生滅門，觀其生滅本不生滅，乃能入真如門也。

Because sentient beings from beginningless time have never been awakened, tathatā in its entire essence becomes arising and ceasing. Abandoning the mind of arising and ceasing, where else could there be tathatā to contemplate? Therefore, one must proceed directly from the aspect of the arising and ceasing of the mind, contemplate that its arising and ceasing is fundamentally unarisen and unceasing, and then one can enter the aspect of tathatā.