In the last two years Ephesians 5 has become very significant. Somehow, previously, I had missed the point of the passage. The point of putting on the whole armour of God is to resist the attacks of Satan! It's unnerving because there is an assumption that Satan exists and that his mode of operation requires being fully dressed, from head to toe in God's protection.
There may be some who scoff at the the idea of an evil presence much less our need to be ready for battle. But, when Jesus walks into the temple in the first chapter of Mark, his first miracle is getting rid of a demon who has taken up residence in the middle of the place of worship. It's a warning that evil is often times present in the places you least expect it. Dressing in full battle gear is the only way to survive.
It's true now and it was true in the fourth century as you will read below. . .
Let us, therefore, take courage and strip ourselves for the contests. Christ has put on us armor that is more glittering than any gold, stronger than any steel, hotter and more violent than any fire, and lighter than any breath of air. The nature of this armor does not burden and bend our knees, but it gives wings to our limbs and lifts them up. If you wish to take flight to heaven, this armor is no hindrance. It is a new kind of armor, since it is a new kind of combat.
Although I am human, I must aim my blows at demons; although clad in flesh, my struggle is with incorporeal powers. On this account God has made my breastplate not from metal but from justice; God has prepared for me a shield which is made not of bronze but of faith. I have, too, a sharp sword, the word of the Spirit.
John Chrysotom, Fourth Century