Sword
The Bible compares the tongue to a lethal weapon: a sword. With a word - through gossip, slander or a negative comment - we can do as much damage to someone's life as we could with the thrust of a sword. This is why we must seek the Holy Spirit's assistance in our lives, asking his aid in showing us how to control our tongues, for "the fruit of the Spirit is...self-control" (Galatians 5:22).

The Bible also compares the Word of God to a sword. The Word of God is able to divide soul and spirit; it cuts through the darkness of evil, exposes secrets and brings truth to light. Called the "sword of the Spirit" in Ephesians, we are told to carry the Word of God in our minds as an offensive weapon; we're encouraged to learn it well, incorporating its living truths into our lives. We are to use the Bible not only to defend our faith, but also to protect ourselves from Satan's lies. The devil also knows the Bible, but he twists it to serve his own purpose (see Matthew 4:1-11). By knowing the truth, we will be better equipped to see through his deceptions.

The Word of God is a sword of instruction and correction for life.
Ephesians 6:17
Hebrews 4:12
Revelation 1:16
Our tongues are compared to swords because of the damage they can do in the lives of others.
Psalm 55:21; 57:14
Proverbs 12:18