首楞嚴義疏注經 9.278

9.278

悔惱種子被激而生，修無方便，故引魔鬼也。如《四分律》，婆求河邊諸比丘等修不淨觀，厭淨過分，求刀自害，魔使之然。悟則無咎。

Seeds of regret and affliction are stirred into arising; practice lacks skillful means, and thus demons and ghosts are drawn in. As in the Four-Part Vinaya (Cāturvargīya-vinaya), where the monks by the Vaggumudā River cultivated the contemplation of impurity, developed excessive revulsion toward purity, and sought knives to harm themselves—it was demons that caused them to do so. If they awaken, there is no fault.