87 At a moment when one is forced to note with sorrow the disproportion between the number of priests and the calls upon them, when one sees that even today the words of Our Savior apply: "The harvest indeed in great, but the laborers are few" ( Saint Matthew ix. 37; Saint Luke x.2), the collaboration of the laity in the Apostolate of the Hierarchy, a collaboration indeed given by many and animated with ardent zeal and generous self-devotion, stands out as a precious aid to the work of priests and shows possibilities of development which justify the brightest hopes. The prayer of the Church to the Lord of the Harvest that he send workers into his vineyard (cf. Saint Matthew ix. 37; Saint Luke x.2) has been granted to a degree proportionate to the present needs, and in a manner which supplements and completes the powers, often obstructed and inadequate, of the priestly apostolate. Numbers of fervent men and women of youth obedient to the voice of the Supreme Pastor and to the directions of their bishops, consecrate themselves with the full ardor of their souls to the works of the apostolate in order to bring back to Christ the masses of peoples who have been separated from Him.
Source: Summi Pontificatus (Vatican.va)