金剛經纂要刊定記 7.126

7.126

無所染者。即無分別不取不動也。此則正是斷疑之意。謂佛所有說皆如真實，傳授之人要皆如是，既如其法福乃無邊，何疑持說無福德耶？又如偈云：「諸佛說法時，不言是化身，以不如是說，是故彼說正。」意云：若言是化則人無敬心，所說之法寧肯信受？由不說故人皆宗奉，所說之教咸悉受持，無漏之福自然無量等。

"Unstained" means non-discrimination, non-grasping, and unmoving. This is precisely the intent of resolving the doubt. It means that everything the Buddha preaches is just like reality, and those who transmit it must also be like this. Since it accords with the Dharma, the merit is boundless; how could one doubt that upholding and preaching has no merit? Furthermore, as the verse says: "When the Buddhas preach the Dharma, / they do not say it is a transformation body; / because they do not preach in this manner, / therefore that preaching is correct." The intent is: if they said it was a transformation body, people would lack reverent minds; how would they be willing to believe and accept the Dharma preached? Because they do not say so, all people revere and honor it, and all uphold the teaching preached, so that untainted merit is naturally immeasurable, and so forth.