In the Sacrament of Holy Orders, or Ordination, the priest being ordained vows to lead other Catholics by bringing them the sacraments (especially the Eucharist), by proclaiming the Gospel, and by providing other means to holiness.
The vocation to ordination is indeed a great sacrament, calling for a deep commitment to the gospel. Even though the ordained may show signs of weakness and sinfulness, in itself this situation would never invalidate the effect of the sacrament he administers. However, the ordained’s calling is such that in all his ministry, he is to cherish and to manifest his discipleship to Jesus Christ.
The priesthood is ministerial. He is called to a life of service, service to God and to the community of believers. Priesthood presents a unique call to become like Jesus and to live out concretely the values of Jesus. When a man says yes to priesthood, he is saying yes to a life of service. To be called to the priesthood is to called to a life of love. To be called to priesthood is to be called to act at times in the name of the whole Church. To be a minister of Christ is to be a minister of the Church.
Only a bishop can confer the sacrament of Holy Orders. This is because Holy Orders is a sacrament of the apostolic ministry, and so it is bishops as successors of the apostles who hand on “the gifts of the Spirit” (cc 1575-1576). The Church considered herself bound by the choice made by the Lord himself of selecting only men as apostles (cc 1577). No one has the right to be ordained nor to claim this office for themselves; rather it is answering a call which comes from God. God has entrusted the Church with the responsibility of discerning who are suitable candidates. Continuing a practice that dates back to the 10th century, ordained ministers of the Latin Church are normally chosen from among men of faith who live a celibate life and who intend to remain celibate “for the sake of the kingdom”. This is a sign of the life of service to which the ordained minister is consecrated (cc 1578-1579).