If we desire one more proof of [the Catholic Church’s] boundless charity, we shall find it in the Redemptive Orders, whose founders were inspired by the most sublime of motives. In Africa and Asia the infidels treated their Christian captives as slaves, who were not seldom in peril of their lives. A number of heroic souls combined in an attempt to deliver these unfortunates: they begged money for ransom, and even visited Moslem territory, offering themselves as substitutes for any captives whose salvation was thought to be in danger. […]
The Ransomers, otherwise known as the Order of Our Lady of Ransom [now Mercedarians], was founded in 1223 by St Peter Nolasco and St Raymond of Pennaforte, who introduced into their Rule the vow of self-substitution for captives. Between the date of their foundation and the French Revolution, these two orders delivered more than 600,000 captives, among whom was Cervantes.
Henri Daniel-Rops, Cathedral and Crusade: Studies of the Medieval Church (1050-1350)