71 With all the more reason, then, does the Catholic Church, most loving mother of all men, call on all her children to be zealous in helping these intrepid missionaries by their offerings, by prayer and by fostering missionary vocations. In motherly fashion she compels them to wear the livery of tender compassion, and to take part, if not in the actual apostolate, at least by zealous cooperation, and not allow the wish of the most loving Heart of Jesus to remain unrealized, who "came to seek and to save what was lost." If they help in any way to bring the light and consolations of the Faith to one hearth, let them understand that a Divine force has been thus released, which will keep on growing in momentum throughout the ages. If they help even one candidate for the priesthood, they will fully share in all the future Masses and in all the fruits of sanctity and apostolic works that will be his. Indeed, all the faithful make up one and the same immense family who, as members of the Church militant, suffering and triumphant, share their benefits with one another. There seems to be nothing more apt than the dogma of the "Communion of Saints" for bringing home to the people the utility and importance of the missions.
Source: Evangelii Praecones (Vatican.va)