124 For the preservation of the moral order neither the laws and sanctions of the temporal power are sufficient, nor is the beauty of virtue and the expounding of its necessity. Religious authority must enter in to enlighten the mind, to direct the will, and to strengthen human frailty by the assistance of divine grace. Such an authority is found nowhere save in the Church instituted by Christ the Lord. Hence We earnestly exhort in the Lord all those who hold the reins of power that they establish and maintain firmly harmony and friendship with this Church of Christ so that through the united activity and energy of both powers the tremendous evils, fruits of those wanton liberties which assail both marriage and the family and are a menace to both Church and State, may be effectively frustrated.
Source: Casti Connubii (Vatican.va)