大乘起信論義記 2.131

2.131

Below, in revealing the gain, if one reaches the source of the mind and attains thoughtlessness, then one comprehensively knows the differences of the four marks in the movements of the One Mind of all sentient beings; hence it says, 'if one attains thoughtlessness, then one knows the mind's arising, abiding, difference, and cessation.' 'Because of the equality of thoughtlessness' explains and establishes the above meaning.