John Cassian, The Institutes VII.22: That one who actually has no money may still be deemed covetous

For it is possible even for one who has no money to be by no means free from the malady of covetousness, and for the blessing of penury to do him no good, because he has not been able to root out the sin of cupidity: delighting in the advantages of poverty, not in the merit of the virtue, and satisfied with the burden of necessity, not without coldness of heart. For just as the word of the gospel declares of those who are not defiled in body, that they are adulterers in heart; so it is possible that those who are in no way pressed down with the weight of money may be condemned with the covetous in disposition and intent. For it was the opportunity of possessing which was wanting in their case, and not the will for it: which latter is always crowned by God, rather than compulsion. And so we must use all diligence lest the fruits of our labours should be destroyed to no purpose. For it is a wretched thing to have endured the effects of poverty and want, but to have lost their fruits, through the fault of a shattered will.