6 See how Peter left his net; see how the publican rose from the receipt of custom. In a moment he became an apostle. “The Son of man has not where to lay his head,” and do you plan wide porticos and spacious halls? If you look to inherit the good things of the world you can no longer be a joint-heir with Christ. You are called a monk, and has the name no meaning? What brings you, a solitary, into the throng of men? The advice that I give is that of no inexperienced mariner who has never lost either ship or cargo, and has never known a gale.
Lately shipwrecked as I have been myself, my warnings to other voyagers spring from my own fears. On one side, like Charybdis, self-indulgence sucks into its vortex the soul's salvation. On the other, like Scylla, lust, with a smile on her girl's face, lures it on to wreck its chastity. The coast is savage, and the devil with a crew of pirates carries irons to fetter his captives. Be not credulous, be not over-confident. The sea may be as smooth and smiling as a pond, its quiet surface may be scarcely ruffled by a breath of air, yet sometimes its waves are as high as mountains.
There is danger in its depths, the foe is lurking there. Ease your sheets, spread your sails, fasten the cross as an ensign on your prow. The calm that you speak of is itself a tempest. “Why so?” you will perhaps argue; “are not all my fellow-townsmen Christians?” Your case, I reply, is not that of others. Listen to the words of the Lord: “If you will be perfect go and sell that you have, and give to the poor, and come and follow me.” You have already promised to be perfect. For when you forsook the army and made yourself an eunuch for the kingdom of heaven's sake, you did so that you might follow the perfect life.
Now the perfect servant of Christ has nothing beside Christ. Or if he have anything beside Christ he is not perfect. And if he be not perfect when he has promised God to be so, his profession is a lie. But “the mouth that lies slays the soul.” To conclude, then, if you are perfect you will not set your heart on your father's goods; and if you are not perfect you have deceived the Lord. The Gospel thunders forth its divine warning: “You cannot serve two masters,” and does any one dare to make Christ a liar by serving at once both God and Mammon?
Repeatedly does He proclaim, “If any one will come after me let him deny himself and take up his cross and follow me.” If I load myself with gold can I think that I am following Christ? Surely not. “He that says he abides in Him ought himself also so to walk even as He walked.”
Source: Letters (New Advent)