大乘起信論義記 2.159

2.159

The first line is the simile of the real turning in accord with the false. Next, water and wind not parting from each other is the simile of the real and false being mutually dependent. Water not being of a moving nature is the simile of the substance of the real being unchangeable; this reveals that it is not moving by its own nature, but moves only in accord with another. From 'if the wind ceases' onward is the simile of putting an end to the false and revealing the real; this clarifies that if it moved by its own nature, then when the moving marks were extinguished the wet nature would be extinguished along with them, but because it moves only in accord with another, when the moving marks are extinguished the wet nature is not destroyed.