金剛經纂要刊定記 4.356

4.356

云何下。指疑起處，便結成疑。此亦從前第三中來，以彼文云：「如來所說法，皆不可取不可說故。」

From "How" downward points out where the doubt arises and then forms the doubt. This also derives from the earlier third [section], because that text states: "The Dharma taught by the Tathāgata can neither be grasped nor spoken."