金剛經纂要刊定記 3.56

3.56

返本下二句，對敷座而坐也。法空即敷座，心寂即而坐，敷座方堪人坐，法空心始得寂。

The two lines beginning "Returning to the origin..." correspond to spreading the seat and sitting down. The emptiness of dharmas is the spreading of the seat; the stillness of the mind is the sitting down. Only after the seat is spread is it fit for one to sit; only after dharmas are empty can the mind attain stillness.