The Institutes, Book 7
How Greed Can Be Conquered
In this case, the greatest victory and a lasting triumph will be, as the saying goes, for the monk’s conscience not to be defiled by owning even the smallest coin. For once a man has been overcome in the matter of a small possession and has admitted into his heart a root of evil desire, it is impossible for him not to be inflamed soon with the heat of a still greater desire. The soldier of Christ will be victorious and safe, and free from all the attacks of desire, as long as this most evil spirit does not plant in his heart a seed of this desire. So, although with every kind of sin we ought as a rule to watch the serpent’s head, in this one above all we should be more keenly on our guard. For if it is admitted, it will grow by feeding on itself and kindle a worse fire for itself. So we must not only guard against owning money but also drive the desire for it out of our souls. We should not so much avoid the results of greed as cut off at the roots every inclination toward it. For it will do no good not to own money if the desire to get it exists in us.