29 Saying these things to yourself, give thanks unto the Lord, that he has made you to be of this part, not hating you, but loving you greatly; since He would not have permitted those men either to suffer thus, if he had not exceedingly loved them, because He made them more illustrious by these evils. There is nothing so good as thanksgiving; even as there is nothing worse than blasphemy. We should not wonder that when we become intent upon spiritual things, we suffer much that is grievous.
For as thieves do not dig through and assiduously keep watch there, where there is hay, and chaff, and straw, but where there is gold and silver; so also the devil besets those especially who are engaged in spiritual matters. Where virtue is, there are many snares! Where almsgiving is, there is envy! But we have one weapon which is the best, and sufficient to repel all such engines as these; in everything to give thanks to God. Tell me, did not Abel, when offering the first fruits to God, fall by the hand of his brother?
But yet God permitted it, not hating one who had honoured him, but loving him greatly; and beside that which came of that excellent sacrifice, providing him another crown by martyrdom. Moses wished to protect a certain one who was injured, and he was put into the extremest peril, and banished his country. This too God permitted, that you might learn the patience of the saints. For if, foreknowing that we should suffer nothing of a grievous kind, we then put our hands to the work of religion, we should not seem to be doing anything great, as having such a pledge of safety.
But as it is, those who do such things are the more to be wondered at, even for this; because, though they foresee dangers, and punishments, and deaths, and ten thousand evils, still they did not desist from those good works, nor become less zealous from the expectation of terrors.
Source: Homilies on the Statues (New Advent)