6:14

the belt of truth: Soldiers of ancient times prepared themselves for battle by fastening a belt around the waist. (Isa 8:9, ftn.) Therefore, “putting on the belt,” or “girding oneself,” was an idiom that meant “prepare for action.” (See study notes on Lu 12:35; 17:8.) Appropriately, then, this is the first part of the armor that Paul mentions in his list. The Roman soldier wore a wide belt of leather with metal plates attached to decorate and stiffen it. With his belt fastened tightly, the soldier was better able to stand firm in battle. He suspended an armored apron from the belt, so that his midsection was protected. Just as a belt can provide support and protection for the soldier, an unbreakable attachment to divine truths can strengthen a Christian to remain firm in the face of trials. The Roman soldier’s sword was usually suspended from his belt and attached by rings. (See study note on Eph 6:17.) Paul’s illustration suggests that Christians need to use the truths of God’s Word as a constant protection against spiritual attack. Christians who clearly understand those truths are protected from false teachings.​—Eph 4:13, 14; 1Ti 2:3-7.

the breastplate of righteousness: Roman soldiers of the first century C.E. used a variety of body armors. One type of breastplate was made of overlapping iron strips attached to leather pieces by means of hooks, straps, and buckles. Such a breastplate offered protection for the vital organs, the heart in particular. In fact, Greek historian Polybius of the second century B.C.E. described this breastplate as “the heart-protector.” Paul saw that Christians have a need to protect their figurative heart. (Compare 1Th 5:8.) Just as that metal armor prevented arrows and swords from piercing the soldier’s heart, so love for God’s righteous principles and standards protects the Christian’s figurative heart. (Ps 119:97, 105; Pr 4:23) Because of sinful inclinations, an imperfect human is always in urgent need of such protection. (Jer 17:9) In the Hebrew Scriptures, Jehovah himself is described as wearing righteousness like armor.​—Isa 59:15, 17.