Jesus Christ is priest, prophet, and king. Through their ordination and its concomitant ontological change, priests are so formed to Christ that it becomes theirs to act as "other Christs" in the triple office of sanctifying (munus sanctificandi), teaching (munus docendi), and governing (munus regendi). It is through their ordination that priests "are configured to Christ in such a way that they are able to act in the person of Christ the head" (Lumen gentium, n. 28 and Presbyterorum ordinis, nn. 2 and 13). The principal realization of action in persona Christi is the confection of the Holy Eucharist. For it is to the Eucharist that "the other sacraments, and indeed all ecclesiastical ministries and works of the apostolate are bound up and directed" (PO, n. 5 and cf. St. Thomas Aquinas, Summa theologiae, III, q. 73, art. 3). It is from the sacrificial altar that the sacramental leadership of the priesthood flows, and it is at the altar that sacramental leadership is manifested.

That same sacramental leadership extends itself to fashion the role of the priest in the life of the Church. It is the priest, as a sharer in Christ’s priesthood, who is not only able to offer the Sacrifice of the Mass, but is also able to extend the healing mercy of God in the Sacraments of Penance and Extreme Unction (Matt 16:18-19 and Jas 5:14-15). It is the priest, as a sharer in Christ’s prophetic mission, who is able to speak in the name of Christ and His Church by preaching and teaching (PO, n. 5). And it is the priest, as a sharer in Christ’s kingship, who may exercise governance so that only a priest may be the pastor of souls or hold the episcopal office (PO, nn. 6 and 7). The indelible spiritual character of ordination enables and facilitates the priest’s responsibility in the sacramental mission of the Church.

In fact, the indelible mark on the souls of priests is a unique sign and symbol of Christ’s continued presence in His Church. As expressed so beautifully in the Letter to the Hebrews, Jesus Christ is the high priest whose singular sacrifice on Calvary effected the salvation of all men once and for all insofar as He offered up Himself (7:26-28). This once-and-for-all sacrifice is re-presented in each and every Mass celebrated by the priests of the Church. Since the Eucharist is "the source and summit of the Christian life" (LG, n. 11), the sacramental leadership of the priest is immediately apparent as he utters the words of consecration and distributes the sacred species to the mystici corporis Christi.

"For priests, as ministers of sacred things, are first and foremost ministers of the Sacrifice of the Mass: the role is utterly irreplaceable, because without the priest there can be no eucharistic offering" (Pastores dabo vobis, n. 48). This utterly irreplaceable role of the priest is the foundation of his part in Christ’s plan for the salvation of the world through the Church. At once, the priest’s role is not only holy but central. It finds its origin and its end in the sacraments, and it finds itself at the epicenter of the divine eucharistic mystery. The priest, then, by virtue of his ordination is a sacramental leader in the Church, an alter Christus, whose sacred duty it is "to proclaim the Lord’s death until He comes" (1 Cor 11:26).