6:17

the helmet of salvation: A Roman soldier’s helmet protected his head, face, and neck. Paul uses the helmet to symbolize a Christian’s hope for salvation by God. (1Th 5:8) As a helmet protects the head, so the Christian’s hope of salvation protects his mind, his thinking faculties. Satan subtly promotes such poisonous influences as selfishness, hatred, and disloyalty. By focusing on the Christian hope​—figuratively wearing hope like a helmet​—the Christian rejects any negative influence on his thinking. (Mr 7:20-22; 2Co 4:4; Re 12:9) Satan also promotes direct persecution, but the hope of salvation helps a Christian maintain his joy even under dire circumstances. (Isa 12:2; Mt 5:11, 12) In the Hebrew Scriptures, Jehovah is said to wear salvation, or victory, as a figurative helmet. (Isa 59:17; ftn.) God keeps ever in mind his intent to save his people and to gain victory.​—Jer 29:11.

the sword of the spirit: The sword, one of the most important weapons used by Roman soldiers, is the only offensive weapon mentioned in Paul’s illustration. (Eph 6:14-17) The Greek word translated “sword” in this verse could refer to a short weapon with at least one sharp edge. The sword used by Roman soldiers was double-edged and designed for close combat. It varied in length but was typically about 60 cm (24 in.) long, and the handle was often fitted with a knob at the end to help the soldier keep hold of his sword. (See Media Gallery, “Roman Sword.”) Many soldiers practiced daily with the sword to become adept at its use. Christians make similar use of “God’s word,” their main weapon for waging spiritual warfare. (2Ti 2:15) Paul was not suggesting that Christians use God’s word to harm others. (Compare 1Pe 3:15.) Rather, they tactfully use Scriptural truths to expose false teachings that mislead people and enslave them spiritually. (Joh 8:32; 17:17; 2Co 10:4, 5) Just as a soldier uses his sword defensively to parry, or block, an enemy’s blows, so Christians use God’s word to protect their minds and hearts against the deceptions of false teachers and against temptations to do wrong.​—Mt 4:1-11; 2Ti 3:16.