An ancient custom still alive today
The practice of providing material support to those charged with preaching the Gospel, thus enabling them to devote themselves completely to their apostolic mission and to care for those in greatest need, is as old as Christianity itself (cf. Acts 4:34, 11:29).
By the end of the eighth century the Anglo-Saxons felt so closely linked to the Bishop of Rome that they decided to send a regular annual contribution to the Holy Father. It was thus that the Denarius Sancti Petri (Alms of Saint Peter) originated and spread throughout Europe.
Like other practices of its kind, this custom underwent many changes in the course of the centuries, until in 1871 Pope Pius IX gave it his approval in the Encyclical Letter Saepe Venerabilis (5 August 1871).
At present the collection is taken up throughout the Catholic world either on 29 June, the Solemnity of Saints Peter and Paul, or on the Sunday closest to this Solemnity