1 The Holy City of God, which is the Church, not being contained within the limits of any State, has from its Founder this infused power that every day it enlarges more and more "the place of its tent," and "stretches out the skins of its tabernacles."(1) But this growth of Christian nations, although it is chiefly caused by the interior breathing and help of the Holy Spirit, is nevertheless brought about externally by the action of men and in a human manner; for the wisdom of God demands that all things should be ordered and brought to their completion in that manner which is fitting to the nature of each. But there is not one only kind of men or of office, by which is brought about the accession of new citizens to this terrestrial Sion. For the first place is that of those who preach the Word of God; Christ taught this by His example and His precepts; the Apostle Paul urged this in these words: "How shall they believe Him of whom they have not heard? And how shall they hear without a preacher? . . . . Faith then cometh by hearing and hearing by the word of Christ."(2) But this office belongs to those who have been duly admitted to minister in sacred things. To them, moreover, those who are wont either to supply help in external matters or to bring down heavenly graces by prayers poured forth to God afford no little help and support. Wherefore the women in the Gospel are praised, who when Christ was preaching the kingdom of God, "ministered unto Him of their substance"(3), and Paul testifies that to those who preach the Gospel has been granted, by the will of God, that they should live of the Gospel.(4) In like manner we know that Christ so commanded His followers and hearers: "Pray ye the Lord of the harvest that he send forth labourers into His harvest,"(5) and that His first disciples, following the Apostles, were accustomed in this manner to address God in prayer: "Grant unto Thy servants that with all confidence they may speak Thy word."(6)
Source: Sancta Dei Civitas (Vatican.va)