15 We repeat again, and still more warmly, that the clergy go to a Christian people tempted on every side, and with every kind of fallacious promise offered by Socialism to apostatize from the true faith. They must therefore submit all their actions to the authority of those whom the Holy Spirit has constituted Bishops, to rule the Church of God, without which would follow confusion and the most grave disorders to the detriment even of the cause they have at heart to defend and promote. It is for this end that we desire that the candidates for the priesthood, on the conclusion of their education in the seminary, should be suitably instructed in the pontifical documents relating to the social question, and the Christian democracy, abstaining, however, as we have already said, from taking any part whatever in the external movement. When they are made priests they will direct themselves with particular care to the people, always the object of the Church's loving care. They will raise the children of the people from the ignorance of things both spiritual and eternal, and with industrious tenderness they will lead them to an honest and virtuous life. They will strengthen the adults in their faith, dissipating the contrary prejudices and confirm them in the practices of Christian life. They will promote among the Catholic laity those institutions which they all recognize as really efficacious in the moral and material improvement of the multitude. Above all they will propose to them the principles of justice and evangelical charity, to which are equally united all the rights and duties of civil and social life, such should be the way in which they fulfil their noble part in the social action.
Source: Fin dal Principio (Vatican.va)