Romans 10:15

15. Sent The first apostles were sent by the visible Christ himself. (Mark 16:15.) And these apostles were to preach and be preachers. And of these apostles, so far forth as they were preachers, every true preacher is a true successor. And here the word sent, applied to every preacher, is the very verb from which the word apostle is formed. (See note on Matthew 10:2.) And every true preacher is sent or apostolized from Christ himself, not visible, yet present; according to his promise to be with his sent preachers to the end of the world. Yet it is not to be held that any preacher, or anybody, is or can be successors of the apostles, or themselves apostles, in the full sense that the first apostles were. As it was necessary that the apostle should have seen Christ, the full apostolate necessarily died with the first apostles. (See note on Luke 1:2.)

Written Isaiah 52:7. To himself and his brother preachers sent forth by Christ, St. Paul exultingly applies those beautiful words of the prophet applied by Jewish commentators themselves to the days of the Messiah. Christ’s heralds are compared to messengers, appearing on the mountains about Jerusalem, bringing good tidings to Zion, the city of David. Their feet, nimbly bringing the joyous bulletin, are called beautiful, because whatever is dear to the heart is apt to seem beautiful to the eye. And these messengers, like Paul himself, were rapid of foot. They were neither sluggard nor settled, but zealous and itinerant.