All Scripture is God breathed, and is useful for teaching, rebuking, correcting and training in righteousness, so that the man of God may be thoroughly equipped for every good work. – 2 Timothy 3:16-17
The Bible is not just some book created by religious scholars centuries ago.  It is the inspired and true Word of God.  It has been tested and proven throughout history.  Every warrior must train, study, and practice to be effective when they fight on the battlefield.  The same is true when being a warrior for Christ.  So read the Bible thoroughly and study it; learn the ways of the Lord and be equipped to practice righteousness in every good work that you do.