It is impossible to enumerate all the forms assumed by Christian charity, or the institutions to which it gave rise. Some of the most curious were devoted to the recovery of prostitutes. This social sore existed throughout the Middle Ages, but increased during the thirteenth century with the growth of towns and universities. Prostitutes were found everywhere, even in the crusading armies! St Louis took steps to regulate their trade, and an encyclical of Innocent III in 1198 promised total remission of his sins to any pious man who married a harlot with a view to her rehabilitation.
In 1204, Fulk, parish priest of Neuilly who was afterwards celebrated as Peter the Hermit of the fourth crusade, began, with his curate Peter of Rossiac, haranguing fallen women in the public squares and in the streets. Later, he founded a congregation for the purpose of reclaiming them; and his devoted efforts soon brought into being an abbey which adopted the Cistercian Rule. Fulk was not alone in this work; in 1272, Bertrand, a citizen of Marseilles, established a similar community which was recognized as a monastic Order by Nicholas III. Their example was imitated at Rome, Bologna, Messina, Bourges, Bijon, and even at St Jean d’Acre in Palestine. But the most interesting and most successful of these undertakings was that of Canon Rudolph of Hildesheim, who was asked by the Archbishop of Mayence to reclaim the fahrende Weiber (street-walkers). He founded the Order of Penitent Sisters of St Magdalen, under whose austere rule these ladies might walk the road to heaven.
Henri Daniel-Rops, Cathedral and Crusade: Studies of the Medieval Church (1050-1350)