28 The four participles fastening … putting on … fitting … taking up … indicate the means by which believers can take their stand against the devil and his schemes. The imperative take in v. 17 communicates another means by which to accomplish the standing, i.e., by the word of God.
29 Grk “girding your waist with truth.” In this entire section the author is painting a metaphor for his readers based on the attire of a Roman soldier prepared for battle and its similarity to the Christian prepared to do battle against spiritually evil forces. Behind the expression “with truth” is probably the genitive idea “belt of truth.” Since this is an appositional genitive (i.e., belt which is truth), the author simply left unsaid the idea of the belt and mentioned only his real focus, namely, the truth. (The analogy would have been completely understandable to his 1st century readers.) The idea of the belt is supplied in the translation to clarify the sense in English.

In other versions

Stand therefore, having fastened on the belt of truth, and having put on the breastplate of righteousness,

Stand firm then, with the belt of truth buckled around your waist, with the breastplate of righteousness in place,

Stand, therefore, with truth like a belt around your waist, righteousness like armor on your chest,

Stand your ground, putting on the belt of truth and the body armor of God’s righteousness.

Stand therefore, girding your waist with truth, and putting on the breastplate of righteousness,

Stand therefore, having your loins girt about with truth, and having on the breastplate of righteousness;

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