首楞嚴義疏注經 10.35

10.35

於勝定中，以心、境二法為所窮處，由是觀成，知二萬劫十方眾生生滅循環不曾散失，如水為氷、氷還成水，雖循環而體不失，故名為常。

In superior samādhi, taking the two dharmas of mind and objects as what is exhaustively investigated, because of this contemplation's completion, he knows that the arising and ceasing of sentient beings in the ten directions over twenty thousand eons cycle without ever dispersing or being lost, like water turning to ice and ice returning to water: although cycling, their essence is not lost; hence he takes it to be permanent.