“It is a vital dimension for the Church,” he explained. “It can happen, however, that the apostolic ardor, the desire to reach others with the good news of the Gospel, diminishes.”

“When Christian life loses sight of the horizon of proclamation, it grows sick,” he continued, “it closes in on itself, becomes self-referential, it becomes atrophied. Without apostolic zeal, faith withers. Mission, on the other hand, is the oxygen of Christian life: it invigorates and purifies it.”

The pope said the way in which Jesus called St. Matthew to leave his former life behind is an example for Christians today.