大乘起信論義記 3.488

3.488

"One who cultivates contemplation should contemplate that all conditioned phenomena of the world do not remain long and change and disintegrate in an instant, and that all mental activities arise and cease from thought-moment to thought-moment, and are therefore suffering. One should contemplate that all phenomena reflected upon in the past are fleeting like a dream; one should contemplate that all phenomena reflected upon in the present are like lightning; one should contemplate that all phenomena reflected upon in the future are like clouds suddenly arising."