The apostolic foundation has this special characteristic: it is both historical and spiritual.
It is historical in the sense that it comes into being through an act of Christ during his earthly existence: the call of the Twelve at the start of his public ministry, their commission to represent the new Israel and to be involved ever more closely with his Paschal journey, which is consummated in the Cross and Resurrection (Mk 1:17; 3:14; Lk 22:28; Jn 15:16). Far from destroying the pre-Easter structure, the Resurrection confirms it. In a special manner Christ makes the Twelve the witnesses of his Resurrection, and they head the list that he had ordered before his death: the earliest confession of Faith in the Risen One includes Peter and the Twelve as the privileged witnesses of his Resurrection (1 Cor).
Those who had been associated with Jesus from the beginning of his ministry to the eve of his Paschal death are able to bear public witness to the fact that it is the same Jesus who is risen (Jn 15:27). After Judas’ defection and even before Pentecost, the first concern of the Eleven is to replace him in their apostolic ministry with one of the disciples who had been with Jesus since his baptism, so that with them he could be a witness of his Resurrection (Acts 1:17-22). Moreover Paul, who was called to the apostolate by the risen Lord himself and thus became part of the Church’s foundation, is aware of the need to be in communion with the Twelve.
This foundation is not only historical; it is also spiritual. Christ’s pass-over, anticipated at the Last Supper, establishes the New Covenant and thus embraces the whole of human history. The mission and task of preaching the Gospel, governing, reconciling, and sanctifying that are entrusted to the first witnesses cannot be restricted to their lifetime. As far as the Eucharist is concerned, Tradition—whose broad lines are already laid down from the first century (see Lk and Jn)—declares that the apostles’ participation in the Last Supper conferred on them the power to preside at the eucharistic celebration.
Thus the apostolic ministry is an eschatological institution. Its spiritual origins appear in Christ’s prayer, inspired by the Holy Spirit, in which he discerns, as in all the great moments of his life, the will of the Father (Lk 6:12). The spiritual participation of the apostles in the mystery of Christ is completed fully by the gift of the Holy Spirit after Easter (Jn 20:22; Lk 24:44-49). The Spirit brings to their minds all that Jesus had said (Jn 14:26) and leads them to a fuller understanding of his mystery (Jn 16:13-15).
The kerygma, if it is to be properly understood, must not be separated or treated in abstraction from the Faith to which the Twelve and Paul came by their conversion to the Lord Jesus or from the witness to him manifested in their lives. – from Catholic Teaching on Apostolic Succession (1973)