金剛經纂要刊定記 4.94

4.94

論云下。約離二執三輪釋上離相，施物是法，施者、受者是人。今皆不見，則離二執名為二空，二空皆離即三輪體空。輪者喻也。如車輪內虛，方能運轉故。《老子》云：「當其無有車之用。」三事體空能招佛果，三體體實即墮世間。斯則以無相輪摧三有相，超出世間也。

Regarding "the treatise states, etc.": this explains the above freedom from marks in terms of relinquishing the two attachments and the three wheels. The gift is a dharma; the giver and the receiver are persons. Now, perceiving neither, one relinquishes the two attachments, which is called the twofold emptiness. Relinquishing both emptinesses is the emptiness of the substance of the three wheels. 'Wheel' is a metaphor: just as a cartwheel must be empty inside in order to turn. Laozi says: 'Where there is nothing, the cart finds its use.' When the three factors are empty in substance, they can bring about the fruit of Buddhahood; if the three substances are taken as real, one falls into the worldly realm. This is using the markless wheel to crush the marks of the three realms of existence and transcend the world.