Ephesians 6:17 - Matthew Poole's English Annotations on the Holy Bible

Take the helmet of salvation: salvation, for the hope of salvation, 1 Thessalonians 5:8. This follows faith, and is of kin to it. Soldiers dare not fight without their helmet: despair, to which the devil tempts us, makes us quit our combat; whereas hope of salvation makes us lift up our heads in the midst of temptations and afflictions. This likewise alludes to Isaiah 59:17. The sword of the Spirit; either the spiritual sword, the war being spiritual, and the enemy spiritual, or rather the sword which the Spirit of God furnisheth us with, and makes effectual in our hands. Which is the word of God; the doctrine of God in the Scripture, called a two-edged sword, Revelation 1:16, Revelation 2:12; which enters into the soul, and divides between the most inward affections, Hebrews 4:12, and cuts the sinews of the strongest temptations, Matthew 4:4,7,10; and conquers the devil, while it rescues sinners from under his power. This relates to Isaiah 49:2.