42 We cannot neglect here to give credit to the work of catechetical organizations, which, in the course of the long history of the Catholic missions, have always given them special, necessary help. There was never a time when catechists were not excellent assistants to missionaries, sharing their labors and relieving them. Our predecessors have openly affirmed that "for the propagation of the Gospel, it is important that their numbers be multiplied," (72) and have stated that their function was "perhaps the most shining example of the apostolate to be carried out by the laity." (73) We, too, while again giving catechists Our warmest praise, exhort them to meditate even more attentively on the happiness of soul which this work brings, and never to cease from making the greatest efforts, under the guidance of the ecclesiastical hierarchy, to cultivate better the study of religion and their own spiritual formation. Catechists must learn from the hierarchy not only the rudimentary elements of the Faith, but also the practice of virtue and a fervent, sincere love for Christ. Instrumental in the establishment and subsequent abundant growth of new Christian communities is the care devoted to increasing the numbers of those who effectively help the ecclesiastical hierarchy, and to perfecting their formation for any other labors they may have to perform in order to carry out their task in the most effective and perfect manner.
Source: Princeps Pastorum (Vatican.va)