Thomas Aquinas — on Ps 9:6 (Exposition on the Psalms of David)

“"The enemy's weapons." Here he explains how the wicked one perished; and he does two things. First, he assigns the cause of his perishing. Second, the manner, at "their memory has perished." The cause of his perishing is that the very thing from which he wished to make a name for himself has perished. For sometimes people make a name for themselves through military power and wars; hence Gen. 6: "These were the mighty men of old, men of renown." Sometimes by building a city: Sir. 40: "The building of a city establishes a name, and above this a blameless wife is accounted"; just as the name of Romulus through Rome. But the Lord destroyed both. "The swords," that is the weapons, "of the enemy," namely of man, "have failed utterly." Ps. 73: "There he broke the powers." "You have destroyed their cities." Is. 1: "Your land is desolate, your cities are burned with fire." This enemy is especially the Devil: Mt. 13: "An enemy has done this." His sword represents temptations. His cities represent evil counsels, which he uses to pervert the good.”