21 To Our beloved Mexican sons We recommend with all Our heart the closest union with the Church and the Hierarchy, manifesting it by their docility to her teachings and directions. Let them not neglect to have recourse to the Sacraments, sources of grace and strength; let them instruct themselves in the truths of religion; let them implore mercy from God on their unhappy nation, and let them make it both a duty and an honour to cooperate with the apostolate of the priesthood in the ranks of Catholic Action.
Source: Acerba Animi (Vatican.va)