IV. Usurious practices forbidden for clergy and for laity.
This point, too, we have thought must not be passed over, that certain possessed with the love of base gain lay out their money at interest, and wish to enrich themselves as usurers. For we are grieved that this is practised not only by those who belong to the clergy, but also by laymen who desire to be called Christians. And we decree that those who have been convicted be punished sharply, that all occasion of sinning be removed.
Source: Letters (New Advent)