金剛經纂要刊定記 5.288

5.288

則如來下。結成疑也。意云：行即是因，菩提是果，既無因行，何得菩提？或不約能得所得以成疑也。前來斷疑則以菩提等行，如今起疑却以行等菩提。

"Then the Tathāgata..." and so forth concludes and forms the doubt. The meaning is: Practice is the cause and bodhi is the fruit; since there is no causal practice, how does one attain bodhi? Or it forms the doubt without relying on the attainer and the attained. Previously, severing doubt equated bodhi with practice, whereas now the arising of doubt conversely equates practice with bodhi.