And therefore by him who is exercising anxious care over the purity of his inner man, those districts should be sought, which do not by their fruitfulness and fertility invite his mind to the trouble of cultivating them, nor drive him forth from his fixed and immovable position in his cell, and force him to go forth to some work in the open air, and so, his thoughts being as it were poured forth openly, scatter to the winds all his concentration of mind and all the keenness of his vision of his aim. And this cannot be guarded against or seen by anyone at all however careful and watchful, except one who continually keeps his body and soul shut up and enclosed in walls, that, like a splendid fisherman, looking out for food for himself by the apostolic art, he may eagerly and without moving catch the swarms of thoughts swimming in the calm depths of his heart, and surveying with curious eye the depths as from a high rock, may sagaciously and cunningly decide what he ought to lure to himself by his saving hook, and what he can neglect and reject as bad and nasty fishes.
Reproduced in full. Translation: Nicene and Post-Nicene Fathers, series 2, vol. 11 (Schaff and Wace, 1894), public domain (Public domain).