俱舍論記 7.54

7.54

「所言三因至作用方興」者，釋第二句。果法至生相，三因方興與果用也。若同類、遍行因，興與等流果用。若異熟因，興與異熟果用。其異熟因，果至生相，過去與果，必無果至生相現在取果。以此明知此頌定約與果用說。

Regarding 'As for the three causes … their function only then arises': this explains the second line. Only when the result dharma reaches the characteristic of arising do the three causes exercise their function of bestowing the result. The similar and omnipresent causes exercise their function of bestowing the outflowing result. The fruition-maturing cause exercises its function of bestowing the fruition-matured result. For the fruition-maturing cause, when the result reaches the characteristic of arising, it bestows the result in the past; under no circumstances does it grasp the result in the present when the result reaches the characteristic of arising. From this, it is clearly known that this verse is definitely spoken with respect to the function of bestowing the result.