俱舍論記 6.12

6.12

「若於此生至無能障用」者，難。若於此法生，彼法應障不障，可得名因。全無障用，設不為障，何得為因？喻況可知。

Regarding '[If this arises, ... has no capacity to obstruct]', this is an objection: If, upon the arising of this dharma, that dharma could obstruct it but does not obstruct it, it could rightly be called a cause. But if it lacks any capacity to obstruct at all, even if it does not obstruct, how can it be a cause? The analogies are understandable.