大方廣圓覺修多羅了義經略疏 2.685

2.685

今修觀之人先以所依之體為本而起觀行。長行云：圓覺清淨無能所，修心宜此，理即禪定義。

Now, persons cultivating contemplation first take the essence relied upon as the foundation and initiate contemplative practice. The prose says: 'Perfect enlightenment is pure, without subject and object; in cultivating the mind, one should accord with this.' The principle is the meaning of dhyāna-samādhi.