大乘起信論裂網疏 3.124

3.124

Nescience causing the mind to move is just like waves arising due to wind; thus the eight consciousnesses and all mental factors are all moving marks. Because nescience ceases, the defiled moving marks cease, but the mind's essence does not cease—just as when the wind calms, the waves cease, yet the water's essence does not cease; thus the mental classes conjoined with the four wisdoms are all like water. If the mind ceasing meant that sentient beings were severed, [it is because] the Tathāgata is called the supreme sentient being; if there were no essence of mind of the four wisdoms to be relied upon, then there would be no nominally designated Tathāgata that can rely upon it.