首楞嚴義疏注經 8.478

8.478

即枉習為因也。枉押成褫，憑虛搆架，勞心役思，撓害無辜，使成有罪。遇明顯境，託以成形，非幽暗類也。走使戰陣，擔砂負石之徒，故云役使。

This is caused by the previously mentioned habit of framing others. Perverting and framing to effect downfall, fabricating falsehoods out of nothing, exhausting mind and straining thought, harassing and harming the innocent to make them guilty. Encountering a distinct and lucid realm, they rely on it to take shape; they do not belong to the gloomy and dark kinds. Running errands on the battlefront, hauling sand and bearing stones—such are they, hence called 'servant ghosts.'