大乘入道次第開決 1.146

1.146

成就八法能淨禪等者。於中道者即是因也。言不依者無託緣也。依託陰等而修禪者。是有所得世間靜慮。非謂真實出世間禪。心無所依與慧平等。是則名為清淨禪矣。

Regarding "accomplishing eight dharmas can purify dhyāna, and so forth": "In the middle way" is the cause. "Not relying" means having no conditioning factor to depend on. Cultivating dhyāna by relying upon the aggregates and so forth is worldly dhyāna with grasping, not true supramundane dhyāna. The mind having nothing to rely upon and being equal with wisdom is called pure dhyāna.