6 As for you, venerable brothers, you are aware of the true nature of the Church, of the constitution which its divine founder gave it, and of the rights and duties associated with it. Nobody can subtract from or destroy these rights and duties. Certainly, the Church is a supernatural society and perfect in its order, as we have recently declared in Our encyclical Immortale Dei . As its purpose is to bring its children to eternal happiness, it has received from God the means and aids to bring them into possession of the heavenly goods. It begins on earth and in the struggles of this life to construct an edifice which will have its final crowning and supreme splendour only in heaven. It is solely the Church's duty to make rules concerning its inner life, whose nature was determined by our Lord Jesus Christ, the restorer of our salvation. Christ ordered that this free and independent power belong to Peter and to his successors, and, under the authority of Peter, to the bishops in their respective churches. This episcopal power includes by its very nature clerical discipline regarding the sacred ministry and the conduct of the priests, for the priests are attached to the bishop like the strings of a lyre.(Ignat. M., epistle to the Ephesians, chap. 15)
Source: Iampridem (Vatican.va)