The phrase "Armor of God" is derived from Ephesians 6:11: "Put on the whole armour of God, that ye may be able to stand against the wiles of the devil.". As a biblical reference, the metaphor may refer to physical armour worn by God in metaphorical battles, or it may refer to vigilant righteousness in general as bestowed by the grace of God : "The night is far spent, the day is at hand: let us therefore cast off the works of darkness, and let us put on the armour of light."

The Epistle to the Ephesians is the tenth book of the New Testament. According to its text, the letter was written by Paul the Apostle, an attribution that Christians traditionally accepted. However, starting in 1792, some scholars have claimed the letter is actually Deutero-Pauline, meaning that it is pseudepigrapha written in Paul's name by a later author strongly influenced by Paul's thought. According to one scholarly source, the letter was probably written "by a loyal disciple to sum up Paul's teaching and to apply it to a new situation fifteen to twenty-five years after the Apostle's death".