Gregory the Dialogist

LITERAL INTERPRETATION. But He shall save the poor from the sword of their mouth, and from the hand of the mighty. For it is this very Poor Man of whom it is said by Paul, Though He was rich, yet for our sakes He became poor. And because the Jews in accusing betrayed the Lord, Whom, when so betrayed, the Gentiles put to death, by 'the sword of the mouth' may be signified the tongue of the Hebrews, that were His accusers, of whom the Psalmist saith, Whose teeth are spears and arrows, and their tongue a sharp sword. …

Morals on the Book of Job, Book VI ↗

Thomas Aquinas

To prove these things seem to happen from divine providence, he goes on to describe what useful purpose they serve. For when the cunning of evildoers is impeded, the poor are freed from their deceptions. This is why he adds, "But he will make the poor safe from the sword of their mouth." For those who are cunning in evil often seduce others by flattering and deceptive language and these words are compared to a harmful sword. …

Commentary on Job ↗