俱舍論記 6.161

6.161

「以諸無為至與果用故」者，答。於生不障可名能作，無取、與用故無有果。應知能作因中有二：一有生用，謂過、現法。二無生用，謂未來法及諸無為，唯無障故名能作因。

Regarding 'Because all unconditioned [dharmas] […] the function of giving results': reply. Being non-obstructive to arising, they can be called kāraṇa[-hetus]; but because they lack the functions of grasping and giving, they have no results. It should be known that within kāraṇa-hetus there are two kinds: first, those with generative function, namely past and present dharmas; second, those without generative function, namely future dharmas and the unconditioned [dharmas], which are called kāraṇa-hetus solely because they are non-obstructive.