起信論疏筆削記 8.57

8.57

約淨等者，覺是淨法，於中有始有本，則隨流時體（本覺）隱用（始覺）廢為滅，反流時體顯用起為生。

Regarding "in terms of pure...": enlightenment is a pure dharma, within which there are actualized and original; thus, when conforming to the flow, essence (original enlightenment) is concealed and function (actualized enlightenment) is discarded, which is "ceasing"; when turning back the flow, essence is manifested and function arises, which is "arising".