-- Ti 1:1-9
"How are they to believe in him of whom they have never heard? And how are they to hear without a preacher? And how can men preach unless they are sent?" No one - no individual and no community - can proclaim the Gospel to himself: "Faith comes from what is heard." No one can give himself the mandate and the mission to proclaim the Gospel. The one sent by the Lord does not speak and act on his own authority, but by virtue of Christ's authority; not as a member of the community, but speaking to it in the name of Christ. No one can bestow grace on himself; it must be given and offered. This fact presupposes ministers of grace, authorized and empowered by Christ. From him, bishops and priests receive the mission and faculty ("the sacred power") to act in persona Christi Capitis; deacons receive the strength to serve the people of God in the diaconia of liturgy, word and charity, in communion with the bishop and his presbyterate. The ministry in which Christ's emissaries do and give by God's grace what they cannot do and give by their own powers, is called a "sacrament" by the Church's tradition. Indeed, the ministry of the Church is conferred by a special sacrament.
-- CCC 875