Leo the Great

The evil of usury must be shunned, and the profit that lacks all human kindness must be avoided. The means for unjust and grievous gain is increased, but the essence of the soul is worn down, since usury in money is the ruin of the soul. The holy prophet David showed what God thinks about the people of this kind when he says, "Lord, who will dwell in your tent, or who will rest on your holy mountain?" Those are taught by the reply of the divine voice, and those know that they have a part in eternal rest if, among the other rules of a holy life, "they do not give their own money at usury." They are shown to be strangers to the "tent" of God and foreign to his "holy mountain" if they seize a deceitful profit for their money by usury, and, while they want to be rich through another's loss, they are worthy to be punished by eternal penury. But you, dearly beloved, who have believed the promises of the Lord with your whole heart, flee the foul leprosy of avarice and make a holy and wise use of God's gifts. Since you enjoy his generosity, take care that you may be able to have companions of your joy. The things that are supplied to you are lacking to many, and in their need the material has been given to you for imitating the divine goodness, so that through you the divine goodness might pass over to others. As you give out your temporal goods well, you are acquiring eternal.