Summary: Starting from the Franciscan Observance and the socio-economic characteristics of the 1400’s, this study underlines the contribution of Bernardine of Siena regarding the activity of some market actors who were his contemporaries. The merchant and the lucrum of commerce are no longer condemned a priori, but are rather considered indispensable to the good of the communitas, where avarice and the unproductive concentration of riches are being defeated. This constitutes and important and eminently Franciscan novum in theological and canonical reflection. Moreover, Franciscan thought here goes beyond the merely theoretical and hortatory, giving birth to the Mons Pietatis, an institution extraordinarily relevant to our own time, as it is compared with today’s microcredit, and one that is capable to make tangible the fruitfulness of the virtuous circulation of wealth, through the creation of civil credit. Economic historiography of the transition from the late Middle Ages to the modern period, as achieved with the Franciscan contribution, is particularly fertile with intuitions and categories that are valid for our time too.