金剛經纂要刊定記 7.216

7.216

難契等者。本為執情堅固不了即空，由是設喻以蕩分別。若觀有體之物便同折色，難悟即空，空觀不成故云難契。

"Hard to accord with," etc.: Originally, because grasping emotions were firmly held and people did not realize immediate emptiness, analogies were devised to clear away conceptual proliferation. If one contemplates things that have substance, it becomes equivalent to reducing form [analytically]; it is difficult to awaken to immediate emptiness, and the contemplation of emptiness fails to form, hence it says "hard to accord with."