John Chrysostom

"Stand therefore," saith he, "having girded your loins with truth." He is not speaking of a literal, physical girdle, for all the language in this passage he employs in a spiritual sense. And observe how methodically he proceeds. First he girds up his soldier. What then is the meaning of this? …

Homilies On Ephesians 23 ↗

Athanasius of Alexandria

At all times let us stand firm, but especially now, although many afflictions overtake us and many heretics are furious against us. Let us then, my beloved brothers, celebrate with thanksgiving the holy feast that now draws near to us, "girding up the loins of our minds," like our Savior Jesus Christ, of whom it is written, "Righteousness shall be the girdle of his loins, and faithfulness the girdle of his reins."

Festal Letter 3 ↗

Thomas Aquinas

368. And justice shall be. Here his constancy in persevering is set out: and justice, which he shall observe in his judgments, shall be the girdle of his loins, that is, the sword with which he shall fight, and faith, confidence from God by which he will prevail; and this can be applied to Christ and to the just kings. Or the girdle of his loins which strongly adheres to man, and girdles the whole man on all sides. …

Commentary on Isaiah ↗

Bonaventure

Finally, He must be supremely just, because of the manifold character of a justice making infallible inquiries, irreproachable distinctions, and irrevocable judgments, handing out retribution to each one according to his deeds. Isaiah writes: "A shoot shall sprout from the stump of Jesse. Justice shall be the band around his waist. Not by appearance shall He judge nor by hearsay shall He decide." Such, then, is God: for if He were mere man, He could not judge otherwise than through witnesses. …

Collations on the Hexaemeron, Collation 3 ↗