“This Sacred Council, following closely in the footsteps of the First Vatican Council, with that Council teaches and declares that Jesus Christ, the eternal Shepherd, established His holy Church, having sent forth the apostles as He Himself had been sent by the Father; and He willed that their successors, namely the bishops, should be shepherds in His Church even to the consummation of the world. And in order that the episcopate itself might be one and undivided, He placed Blessed Peter over the other apostles, and instituted in him a permanent and visible source and foundation of unity of faith and communion. And all this teaching about the institution, the perpetuity, the meaning and reason for the sacred primacy of the Roman Pontiff and of his infallible magisterium, this Sacred Council again proposes to be firmly believed by all the faithful. Continuing in that same undertaking, this Council is resolved to declare and proclaim before all men the doctrine concerning bishops, the successors of the apostles, who together with the successor of Peter, the Vicar of Christ, the visible Head of the whole Church, govern the house of the living God.
Bishops, therefore, with their helpers, the priests and deacons, have taken up the service of the community, presiding in place of God over the flock, whose shepherds they are, as teachers for doctrine, priests for sacred worship, and ministers for governing. And just as the office granted individually to Peter, the first among the apostles, is permanent and is to be transmitted to his successors, so also the apostles’ office of nurturing the Church is permanent, and is to be exercised without interruption by the sacred order of bishops. Therefore, the Sacred Council teaches that bishops by divine institution have succeeded to the place of the apostles, as shepherds of the Church, and he who hears them, hears Christ, and he who rejects them, rejects Christ and Him who sent Christ.
21. In the bishops, therefore, for whom priests are assistants, Our Lord Jesus Christ, the Supreme High Priest, is present in the midst of those who believe. For sitting at the right hand of God the Father, He is not absent from the gathering of His high priests, but above all through their excellent service He is preaching the word of God to all nations, and constantly administering the sacraments of faith to those who believe, by their paternal functioning. He incorporates new members in His Body by a heavenly regeneration, and finally by their wisdom and prudence He directs and guides the People of the New Testament in their pilgrimage toward eternal happiness. These pastors, chosen to shepherd the Lord’s flock of the elect, are servants of Christ and stewards of the mysteries of God, to whom has been assigned the bearing of witness to the Gospel of the grace of God, and the ministration of the Spirit and of justice in glory.”
Lumen Gentium , the Dogmatic Constitution of the Church, Vatican II