The Saving and the Ruinous Sword

Qui das salutem regibus, qui liberas David servum tuum de gladio maligno. Reges, homines justos significat et veraces, qui regunt, ut diximus, adjutorio Domini corpora sua. Istis ergo regibus Dominus dat salutem cum eos a vitiis carnalibus liberos facit; de quibus in Sapientia dicitur: Dat regnum regibus. Liberas David, ad pugnam respicit Goliae; ut qui liberatus fuerat corporaliter, spiritualiter victor esset immanium quoque vitiorum. De gladio maligno, diaboli significat potestatem. Quia et Domini gladius legitur; sed illum benignum esse non dubium est, sicut dicit in Evangelio: Non veni pacem mittere in terram, sed gladium. Quapropter malignus est gladius diaboli, quia dividit a bonis; benignus est autem gladius Domini, quoniam separat a malis. Cassiodorus, Expositio In Psalterium, Psalmus CXLIII Source: Migne PL 70.1019a-b

You who give salvation to kings, who freed your servant David from the wicked sword... 1 'Kings,' signifies righteous and true men, who rule, as we have said, their bodies by the help of the Lord. Therefore to these kings the Lord gives salvation when he frees than from carnal vices, concerning which it is said in Wisdom: 'He gives the kingdom to kings.' 2 'He who freed,' looks to the fight with Goliath, so that he who was freed bodily, may also be a victor spiritually over monstrous vices. The wicked sword signifies the power of the devil. Because even the Lord has a sword, it is said, but this is undoubtedly one that is kindly, as it says in the Gospel: 'I have not come to bring peace to the earth, but a sword.' 3 Whence the sword of the devil is wicked, because it cuts one off from goods, but the sword of the Lord is benign because it separates one from evils. Cassiodorus, Commentary On The Psalms, from Psalm 143 1 Ps 143.10 2 Wisd 9.7 3 Mt 10.34