成唯識論演祕 6.190

6.190

論云所緣法者，即是因法，既云所緣，必須有體，故所緣因除彼空花。疏云以是法者，以是法緣法也，省所緣言，但云是法。

The Treatise speaks of 'dharma that is an ālambana', which is the causal dharma. Since it says 'ālambana', it must have real substance; therefore, the reason 'ālambana' excludes that sky-flower. When the Commentary says 'because it is a dharma', it means 'because it is the dharma of being an ālambana-pratyaya dharma'; it simply omits the word 'ālambana' and merely says 'it is a dharma'.