Gregory the Dialogist

LITERAL INTERPRETATION. And so the needy shall have hope. And iniquity shall stop her mouth. For when the poor man is rescued, 'the needy' is restored to hope, for the lowly people of the faithful is shaken with dismay at our Redeemer dying, but is established firm by His rising again, for the very first poor ones of His people, viz. the chosen Preachers, were smitten by the sight of His death, but restored by the manifesting of His resurrection. …

Morals on the Book of Job, Book VI ↗

Thomas Aquinas

Two things follow from this. One is that men, who are powerless in their own right must confide in divine power because God has care over human affairs, and so he says, "he will be the hope of the poor." The other is that powerful and evil men hold themselves back lest they be totally ruined and so the text continues, "and injustice will shut her mouth," i.e. so that it does not completely waste itself in the harm of others.

Commentary on Job ↗