大乘起信論義記 3.489

3.489

First is the contemplation of impermanence. Second, from 'all mental activities' onward, clarifies the contemplation of suffering. Third, from 'One should contemplate' onward, clarifies the contemplation of non-self. Therein, the past has no substantiality and is hard to pursue; the present does not abide for a kṣaṇa; the future originally has no accumulation, but only suddenly exists through the assembly of conditions, not having come from the ten directions.