佛遺教經論疏節要 1.121

1.121

可畏者，招感生死無解脫期。既皆由心，安得不畏？毒蛇喻瞋心，對違境。惡獸喻癡心，對中庸境。怨賊喻貪心，對順境。三毒為害過蝮蛇等，故云甚於。大火遍燒以喻等分，等分越逸亦過大火，故未足喻。

"Frightful" refers to beckoning and karmically inducing saṃsāra without any date of liberation. Since all arises from the mind, how could one not fear it? The venomous serpent symbolizes the mind of hatred, which corresponds to adverse sensory objects. The savage beast symbolizes the mind of delusion, which corresponds to neutral sensory objects. The hostile bandit symbolizes the mind of greed, which corresponds to agreeable sensory objects. The harms of the three poisons exceed those of vipers and the like, and hence it says "more [frightful] than." The raging fire burning everywhere symbolizes the equal combination [of the three poisons]; the breaking loose of the equal combination also exceeds a raging fire, and thus "surpasses what any metaphor can convey."