2 These two offices which consist in giving and in praying are both very useful in extending wider the borders of the Kingdom of heaven, and also have this property, that they can easily be fulfilled by men of all ranks. For who is there of such slender fortune that he is hindered from giving at one time or other a small alms, or occupied by so many things that he cannot pray to God for the messengers of the Holy Gospel? Apostolic men have ever been accustomed to use helps of this kind, particularly the Roman Pontiffs, on whom especially devolves the care of propagating the Christian Faith; although the method of collecting these supplies has not always been the same, but varied and diverse, according to the variety of places and the diversity of times.
Source: Sancta Dei Civitas (Vatican.va)