The Sword of the Spirit
When Paul wrote the letter to the Ephesian congregations that ended up in the Bible, his last instructions before the greetings at the end of the letter were about being clothed in Christ as armor. He told them to use His righteousness and His truth and His faith and His peace as their protection. They should pray in (under the influence and leadership of) the Holy Spirit and use His word as a weapon against evil. See Ephesians 6:10-18.
He identified the sword in his picturesque instructions as the Word of God. Someone wrote to Hebrew believers that God’s Word is sharper than any double-edged sword, and said that it was able to discern thoughts and intentions, able to divide between joints and marrow, and between the soul and the spirit (Hebrews 4:12). It can position itself between places that give life and places that need life.
Jesus used quotes from His Father to combat satan in His temptation experiences in the desert. Knowing and believing what Yahweh had said and prophesying it at the right moments caused Him to get through the desert in 40 days instead of 40 years.
When we get better at using things God has said as weapons against His enemies and as healing tools toward the people He died to save, this double-edged sword will bring His people Life and His enemies destruction.