俱舍論記 6.217

6.217

「即由無障至如應當思」者，答。因若為障，果不得生。由因無障，果方得起，故名增上。此即通能作因。「或能作因」下，別出勝用。

Regarding "Precisely through non-obstruction ... should be contemplated accordingly": the answer. If the cause were an obstacle, the fruit could not arise. Because the cause presents no obstacle, only then can the fruit arise; hence it is called sovereign. This applies generally to the efficient cause. Below, from "Or, the efficient cause ..." its superior active function is separately set forth.