Gregory the Great — as excerpted in the Catena Aurea on Luke 10:3-4

“(ubi sup.) If any one would have these words taken also allegorically, the money shut up in a purse is the hidden wisdom. He then who has the word of wisdom, and neglects to employ it for his neighbour, is like one who keeps his money tied up in his purse. But by the scrip is meant the troubles of the world, by the shoes (made of the skins of dead animals) are signified the examples of dead works. He then who undertakes the office of preacher ought not to bear the burden of business, lest while this presses down his neck he should not rise to the preaching of heavenly things; nor ought he to behold the example of foolish works, lest he think to shield his own works as by dead skins, that is, lest because he observes that others have done these things, he imagine that he also is at liberty to do the same.”