The sword of the spirit is mentioned in Ephesians 6:17: "take the helmet of salvation, and the sword of the Spirit, which is the word of God." This sword is the last piece of armor Paul describes in talking about the armor of God and is the only offensive weapon depicted. Scripture tells us that the sword of the spirit is the word of God. But what exactly is the word of God, and why is it an effective sword?
The word of God refers to God's written Word, the incarnate Word (Jesus as Logos; see John 1:1-14), and His spoken word. For us, this means that the best offense in spiritual warfare is the truth of the Bible, the reality of our salvation in Christ, and what the Holy Spirit reveals to us (John 14:16-17, 26).
We are told that the Bible is God-breathed (2 Timothy 3:16). We also know that when God breathes, life comes into existence (Genesis 2:7). The Word of God is powerful. He created all things out of nothing by simply speaking. We are told in Isaiah 55:10-11 that God's Word does not return void. Hebrews 4:12 says "For the word of God is living and active, sharper than any two-edged sword, piercing to the division of soul and of spirit, of joints and of marrow, and discerning the thoughts and intentions of the heart." God's Word is truth and in it there is great power.
The sword can also be used as a defensive weapon to protect us from the lies of the enemy. Satan is the "father of lies" (John 8:44). When we know the truth, we are able to defend against his lies. Jesus demonstrated this use of Scripture during His desert temptation (Luke 4:1-13). Each time Satan tempted Jesus, He responded with the truth of Scripture.
The sword is also used defensively in the way it assures us of our salvation. Because of Jesus' work on the cross, we know the ultimate victory belongs to God. Jesus as the incarnate Word has conquered our enemy (Hebrews 2:14-15). And the Bible, the written Word, declares it to be so.
The Holy Spirit reveals God's truth to us. Jesus explained, "When the Spirit of truth comes, he will guide you into all the truth, for he will not speak on his own authority, but whatever he hears he will speak, and he will declare to you the things that are to come. He will glorify me, for he will take what is mine and declare it to you. All that the Father has is mine; therefore I said that he will take what is mine and declare it to you" (John 16:13-15). The Holy Spirit gives us power and reveals truth to us (2 Timothy 1:13-14). He dwells in us and is our defender in spiritual warfare.
In order to use a sword to its fullest effect, a soldier must be trained with it. We, too, should be trained in the word of God. This is why memorizing Scripture and cultivating a sensitivity toward the Holy Spirit are important. If we do not know the way our sword works, it will do us little good in battle.