Luke 9:2

Hence also miracles were added to the holy preachers, so that the power displayed might give faith to their words, and that those who preached new things might do new things. When the world was flourishing, when the human race was increasing, when the flesh was subsisting long in this life, when the abundance of things was overflowing, who upon hearing would believe that there was another life? Who would prefer invisible things to visible things? But when the sick were returning to health, when the dead were rising to life, when lepers were receiving cleanliness of flesh, when demoniacs were snatched from the power of unclean spirits, with so many visible miracles performed, who would not believe what he heard about invisible things? For visible miracles shine forth for this purpose: that they may draw the hearts of those who see them to faith in invisible things, so that through what is done wondrously on the outside, what is within may be perceived to be far more wondrous.

Now let us hear what is commanded when the preachers are sent. "Go and preach, saying: The kingdom of heaven is at hand." This, dearest brothers, even if the Gospel were silent, the world proclaims. For its ruins are its voices. For the world, which has fallen from its glory after being worn down by so many blows, shows us, as it were, from close at hand, another kingdom that follows. It is already bitter even to those by whom it is loved. Its very ruins proclaim that it should not be loved. For if a shaken house threatened to collapse, whoever lived in it would flee; and one who had loved it while it stood would hasten to withdraw as quickly as possible from it as it falls. If therefore the world is falling and we embrace it by loving it, we wish to be crushed rather than to dwell in safety, because no reasoning separates us from its ruin when love binds us to its sufferings. It is easy, therefore, now when we see all things destroyed, to separate our heart from love of it. But this was most difficult at that time when they were sent to preach the invisible kingdom of heaven while they saw earthly kingdoms flourishing far and wide on every side.