俱舍論記 20.39

20.39

「若許作用至有此過失」者，說一切有部救，釋無異。若許作用異法體者，可有用無窮及有用常失。然我說用與體無異，隨體說故，體無無窮故用亦無無窮，體非常故用亦非常。汝經部師故不應言有此過失。

Regarding "If it is accepted that activity [...] has this fault": This is the Sarvāstivādin defense, explaining that there is no difference [between activity and entity]. If it were accepted that activity is distinct from the entity of the dharma, the faults of an infinite regress of activities and the permanence of activity could indeed follow. However, I say that activity is not distinct from the entity; it is spoken of in accordance with the entity. Because the entity is free from an infinite regress, the activity is also free from an infinite regress; because the entity is not permanent, the activity is also not permanent. Therefore, you Sautrāntika master should not say that there is this fault.