79 And here Our thoughts turn gladly to that Catholic Action, so much desired and promoted and defended by Us. For by Catholic Action the laity share in the hierarchical apostolate of the Church, and hence it cannot neglect this vital problem of priestly vocations. Comfort has filled Our heart to see the associates of Catholic Action everywhere distinguishing themselves in all fields of Christian activity, but especially in this. Certainly the richest reward of such activity is that really wonderful number of priestly and religious vocations which continue to flourish in their organizations for the young. This shows that these organizations are both a fruitful ground of virtue, and also a well-guarded and well cultivated nursery, where the most beautiful and delicate flowers may develop without danger. May all members of Catholic Action feel the honor which thus falls on their association. Let them be persuaded that, in no better way than by this work for an increase in the ranks of the secular and regular clergy, can the Catholic laity really participate in the high dignity of the "kingly priesthood" which the Prince of the Apostles attributes to the whole body of the redeemed.
Source: Ad Catholici Sacerdotii (Vatican.va)