Moralia in Job 170

In the same place. — And having rent their garments, they sprinkled dust upon their heads toward heaven. They are rent into many parts. — By the garments of the Church we understand all the faithful; whence it is also said through the prophet: With all these shalt thou be clothed as with an ornament. So the garments of the heretics are all those who, concordantly cleaving to them, are wrapped up in their errors. But the heretics have this as their own, that in the very degree in which they go out from the Church, they cannot long stand; but daily they rush to worse things, and, by holding worse opinions, they are rent into many parts, and for the most part are divided farther from their very selves by the altercation of their own confusion.

Since therefore they tear those whom they join to their own perfidy still further into much division, it is rightly said that the friends who come rend their garments. But when the garments are rent, the body is displayed, because often, when the followers are rent asunder, the malice of their thought is laid open; so that discord discloses the deceits which a grievous fault of prior concord shut up. They savour of earthly things from heavenly words. — But they sprinkle dust upon their heads toward heaven. What is understood by dust, if not earthly intelligence? What is designated by the head, if not that which is our principal part, namely the mind? What is expressed by heaven, if not the precept of supernal utterance?

To sprinkle dust upon the head toward heaven, therefore, is to corrupt the mind with worldly understanding, and to savour of earthly things from heavenly words. But they for the most part discuss the divine words more than they grasp them. They sprinkle dust upon their heads, therefore, because in the precepts of God they strive, through earthly intelligence, beyond the powers of their own minds.