金剛經纂要刊定記 5.164

5.164

於證下。述疑意兼指疑起處也。此從前第三第七中來，以彼校量內外財施，不及持經以此得菩提，故遂起疑云：若然者，且言說是因，因即是道，以此證果，理則不成。何者？以果是無為，無為有體，因是有為，有為無體，無體之道不到果中，云何說此而為因耶？

'Regarding realization...' and so forth recounts the meaning of the doubt and also indicates where the doubt arises. This comes from the third and seventh sections above: because those sections compared internal and external material giving as inferior to upholding this sūtra to attain bodhi thereby, a doubt consequently arose, saying: 'If so, then words are a cause, and the cause is the path; using this to realize the fruit is logically untenable. Why? Because the fruit is asaṃskṛta, and the asaṃskṛta has real substance, whereas the cause is saṃskṛta, and the saṃskṛta lacks real substance. A path that lacks real substance cannot reach into the fruit; how can this be spoken of as the cause?'