首楞嚴義疏注經 3.414

3.414

破和合無因也。動寂不同，故云性隔。心即是性，文變故爾。

This refutes blending, combining, and causelessness. Motion and quiescence are not the same; hence it is said that their 'natures are disparate'. 'Mind' (xin) here is just 'nature' (xing); the phrasing merely varies.