大乘起信論廣釋卷第三．四．五 4.132

4.132

論。若如來藏至無是處故　釋曰。此返破愚執也。若體有染。聖應起惑。聖會此時既無惑染。故如來藏體無染也。

[Treatise:] If the tathāgatagarbha [itself possessed characteristics of defilement, causing the holy ones who have attained realization to still have defilements, then that] would be impossible—
[Commentary:] "Explication": This turns back to refute the foolish attachment. If the substance possessed defilements, the holy ones should give rise to afflictions. Since the holy ones, at the time they realize this, are without afflictions and defilements, the substance of the tathāgatagarbha has no defilement.