Ephesians 6:14

στῆτε οὖν therefore stand – Because of what Paul has already said regarding the nature of the battle, the nature of our tools, purpose, and certainty we obtain when we take them up, we are to actively do so. Although not as explicit in some other texts,[ref]See Philippians 2:13[/ref] the interplay between God’s actions and ours is on full display in this transition. We take up the armor of God, which means that we put on Christ victory is guaranteed. However, we still work out and walk out that victory.

περιζωσάμενοι τὴν ὀσφὺν ὑμῶν ἐν ἀληθείᾳ bind the waist in truth – The translation “belt of truth” is an interpretation of the text that is inferred from an idiomatic phrase. Literally, we are to bind our abdomen with truth. The Greek word όσφύς refers to the lower back. The image here is a binder that helps maintain stability during action. Similar to a belt used when lifting heavy weights, truth here gives us stability and structure to prepare us for action. The idiomatic phrase gird your loins “means to be in readiness for anything.”[ref]Spiros Zodhiates, “Όσφύς Osphús,” The Complete Word Study Dictionary: New Testament.[/ref]

καὶ ἐνδυσάμενοι τὸν θώρακα τῆς δικαιοσύνης and dress yourself with the breastplate of righteousness – The concept that the armor of God simply is Christ is nowhere more clearly represented than it is in this phrase. Paul uses the word ἐνδύω endúō in Romans 13:14 and Galatians 3:27 to describe union with Christ. Elsewhere in Scripture, this word describes the act of clothing oneself in the literal sense. Paul is saying the same thing here. Paul is not commanding us to use righteousness to protect ourselves, but to put on Christ. The Greek here makes this clear in that the word δικαιοσύνης is not an adjective but a qualitative noun. Rather than saying that we put on a righteous breastplate, we put on the breastplate that is righteousness.

When we understand this in conjunction with the previous clause, as the copulative καὶ requires us to do, we are commanded to be prepared for readiness by binding ourselves to the truth and being united to Christ.