Ephesians 3:16

The He would grant you, according to the riches of His glory, to be strengthened with might through His Spirit in the inner man.

Just like a child that needs to be fed good food to grow up strong so do our spirits need to be fed the excellent word of the bible.  Our spirits need the leadership that God provides from His word.  The word is knowledge and power for us to increase and reign in this life.  Strengthen the inner man, and our faith strengthens with revelations of Jesus Christ.