Ephesians 6

As Paul compared our fight against darkness and wickedness to war, he counsels -

"Put on the whole armour of God, that ye may be able to stand against the wiles of the devil."  (New Testament | Ephesians 6:11)

As he described the individual components of the  armor of God, he writes of

"...the sword of the Spirit, which is the word of God..."  (New Testament | Ephesians 6:17)

Where the other components protect the body, it is the sword that fights against the wicked.  The word of God taught by the Spirit cuts through the lies and falsehoods that is so prevalent in the world.  Of the "sword" Paul continued to write -

'...for me, that utterance may be given unto me, that I may open my mouth boldly, to make known the mystery of the gospel,
20 For which I am an ambassador in bonds: that therein I may speak boldly, as I ought to speak.'  (New Testament | Ephesians 6:19 - 20)

The only way one can speak the word of God by the Spirit, boldly, is if one studies the word of God.