John Calvin 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. Now follows a description of the armor they were instructed to wear. We must not, however, inquire very minutely into the meaning of each word, for an allusion to military customs is all that was intended. Nothing can be more futile than the extraordinary efforts some have taken to discover the reason why righteousness is made a breastplate instead of a girdle. Paul’s purpose was to touch briefly on the most important points required in a Christian and to adapt them to the comparison he had already used.

Truth, which means sincerity of mind, is compared to a girdle. Now, a girdle was, in ancient times, one of the most important parts of military armor. Our attention is thus directed to the fountain of sincerity; for the purity of the gospel ought to remove from our minds all guile and from our hearts all hypocrisy. Secondly, he recommends righteousness and desires that it should be a breastplate for protecting the breast. Some imagine that this refers to a freely bestowed righteousness, or the imputation of righteousness, by which pardon of sin is obtained. But such matters ought not, I think, to have been mentioned here, for the subject now under discussion is a blameless life. He urges us to be adorned, first, with integrity, and next with a devout and holy life.