1 Samuel 13:19

Moreover, a blacksmith was not to be found, etc. It is indeed clear what chiefly provides the enemy the space to ravage the land of promise, that is, the virtues of the Church: namely, if it lacks a teacher and the maker of spiritual arms, which the Apostle teaches are to be held against the fiery darts of the wicked. For the wicked tempters take great care, as much as they can, that we do not put on the armor of God, so that double-edged swords do not appear in our hands to exact vengeance upon them (Eph. VI).

For, as a result of the king's sin [Saul's offering of the sacrifice], fear had pervaded the whole army. The camp of the enemy, which was lying at no great distance, showed them how real the danger was, and no one had the courage to think of going out to battle: most had absconded to the marshes. For besides the lack of courage on the part of those who felt that God was alienated from them on account of the king's sin, the army was in the greatest need of iron weapons; so much so that nobody, except Saul and Jonathan his son, is said to have possessed either sword or spear. For the Philistines, as conquerors in the former wars, had deprived the Hebrews of the use of arms, and no one had had the power of forging any weapon of war or even making any implement for rural purposes.

30. All these things are indeed described so that the manner of the victory that followed might be made clear. For armed men were conquered by the unarmed, so that everything that is overcome might be attributed to the praises of Almighty God. But if we pursue these things spiritually in our customary manner, we will not find them devoid of mysteries. What then does it mean when it says: "No blacksmith was found in Israel," except that for spiritual battles we are instructed not through secular letters but through divine ones? For no blacksmith is found in Israel because the faithful who see the Lord do not fight against malign spirits by the art of secular knowledge. For they would conquer aided by the blacksmith's art if they prevailed against hidden enemies by the weapons of secular eloquence. And indeed this learning of secular books, even if by itself it does not benefit the spiritual conflict of the saints, when it is joined to divine Scripture, one is more subtly instructed in the knowledge of that same Scripture. Liberal arts are to be learned for this purpose alone: that through instruction in them the divine utterances may be understood more subtly. From the hearts of some, malign spirits remove the desire for learning, so that they neither know secular things nor reach the heights of spiritual things. Therefore it is rightly said: "The Philistines had taken care lest the Hebrews should make sword or spear." The demons clearly know that when we are instructed in secular letters, we are aided in spiritual matters. When therefore they dissuade us from learning these things, what else do they guard against except that we might make a spear or sword? Let the prophet therefore declare the history and make known the zeal of the elect, and let him explain: "Israel went down to the Philistines so that each might sharpen his plowshare or his hoe." We go down to the Philistines when we incline our mind to learning secular books. And it is called a descent because Christian simplicity is on high. But what does it mean that secular letters are said to be on the plain, yet their manner of teaching is lofty? Because although they narrate nothing heavenly, they unfold what they set forth in a marvelous order of speech, and they are elevated by their narration, yet brought low by speaking of carnal things. Whoever desires to know this manner of speaking or…