Finally, be strong in the Lord and in the strength of his might. Put on the whole armor of God, that you may be able to stand against the schemes of the devil.
– Ephesians 6:10-11
Put on the whole armor. God has furnished us with various defensive weapons, provided we do not indolently refuse what is offered. But we are almost all chargeable with carelessness and hesitation in using the offered grace; just as if a soldier, about to meet the enemy, should take his helmet, and neglect his shield. To correct this security, or, we should rather say, this indolence, Paul borrows a comparison from the military art, and bids us put on the whole armor of God. We ought to be prepared on all sides, so as to want nothing. The Lord offers to us arms for repelling every kind of attack. It remains for us to apply them to use, and not leave them hanging on the wall. To quicken our vigilance, he reminds us that we must not only engage in open warfare, but that we have a crafty and insidious foe to encounter, who frequently lies in ambush; for such is the import of the apostle’s phrase, the wiles of the devil.
– John Calvin