John Gill Commentary Ephesians 6:14

"Stand therefore, having girded your loins with truth, and having put on the breastplate of righteousness," — Ephesians 6:14 (ASV)

Stand therefore
Keep your ground, do not desert the army, the church of Christ, nor his cause; continue in the station in which you are placed, keep your post, be upon your watch, stand upon your guard:

having your loins girt about with truth ;
by which is meant the Gospel, and the several doctrines of it; see (Ephesians 1:13) (4:15) ; and to have the loins girt with it, shows, that it should be near and close to the saints, and never departed from; and that it is a means of keeping them close to God and Christ, and of strengthening them against the assaults and attacks of Satan; and is of great use in the Christians' spiritual conflict with their enemies; the girdle is a part of armour, and so considerable as sometimes to be put for the whole, (Isaiah 5:27) ; and here it is mentioned in the first place:

and having on the breastplate of righteousness ;
in allusion to (Isaiah 59:17) , meaning not works of righteousness done by men, though these are a fence when rightly used against the reproaches and charges of the enemy, as they were by Samuel, (1 Samuel 12:3) , but rather the graces of faith and love, (1 Thessalonians 5:8) , though faith has another place in the Christian armour, afterwards mentioned; wherefore it seems best to understand this of the righteousness of Christ, which being imputed by God, and received by faith, is a guard against, and repels the accusations and charges of Satan, and is a security from all wrath and condemnation.