While on earth He exercised the triple office of Priest, Prophet or Teacher, and King. Now as He prepared to leave them for heaven whence He came, He deputed that triple office to His Apostles: the priestly office in bidding them renew the Memorial of His death and by conferring on them the power to forgive sins; the prophetic or teaching office, by promising to send them the Spirit of Truth Who would recall to their minds all things He had taught them and would keep them one in faith; and the kingly office, by giving them a Kingdom (as His Father had given Him a Kingdom), over which they had the powers of binding and loosing. Leaving no doubt that the purpose of His coming was to prolong His Priesthood, His Truth and His Kingship, He consigned His Apostles to the world:

You, therefore, must go out,
Making disciples of all nations,
And baptizing them in the name of the Father And of the Son, and of the Holy Ghost, Teaching them to observe all the commandments
Which I have given you. MATTHEW 28:19-20

If this commission were given solely for the time span of the Apostles, it is evident that they could not possibly go to all nations. The dynamism or current that was passed into the Apostles under the headship of Peter was to continue until Christ’s Second Coming. No doubt was left concerning the authority and the work of the Church when the Master would leave the earth. That day the Propagation of the Faith came into being. No longer were the Apostles and their successors to consider themselves solely as masters in Israel; from now on the whole world was theirs. Nor were they merely to teach; for He Who gave the commission was not just a teacher. They were to make disciples in every nation; and discipleship implied surrender of heart and will to the Divine Master. The power of His redemptive Cross would be in vain unless His servants used it to incorporate other human natures unto Himself. – from Life of Christ (1958)