43 This mission, or "sending forth," embraces "all nations . . . even unto the consummation of the world" and certainly did not cease with the death of the Apostles. Nay, it still continues in the bishops who are in communion with the Vicar of Jesus Christ. For in them, as being specifically named "those who are sent," namely, Apostles of the Lord, the fullness of the apostolic dignity resides, which as St. Thomas Aquinas testifies "is the chief dignity in the Church." That apostolic fire which Jesus Christ brought upon the earth must issue from their hearts and inflame the hearts of all Our faithful children and arouse in them fresh zeal for the missionary tasks of the Church everywhere.
Source: Fidei Donum (Vatican.va)