10 Wherefore, to use the words of the Holy Pontiff, "Turn your steps towards this unshaken rock upon which Our Savior founded the Universal Church, so that the path of him who is sincere of heart may not be lost in devious windings" ( Reg . viii. 24, ad Sabin. episcop.). It is only the charity of the Church and union with her which "unite what is divided, restore order where there is confusion, temper inequalities, fill up imperfections" ( Registr . v. 58 (53) ad Virgil. episcop.). It is to be firmly held "that nobody can rightly govern in earthly things, unless he knows how to treat divine things, and that the peace of States depends upon the universal peace of the Church" ( Registr . v. 37 (20) ad Mauric. Aug.). Hence the absolute necessity of a perfect harmony between the two powers, ecclesiastical and civil, each being by the will of God called to sustain the other. For, "power over all men was given from heaven that those who aspire to do well may be aided, that the path to heaven may be made broader, and that earthly sovereignty may be handmaid to heavenly sovereignty" ( Registr . iii. 61(65) ad Mauric. Aug.).
Source: Iucunda Sane (Vatican.va)