Comments:

In the context here, the word of God is none other than Jesus Christ.  Also called the word of God in John 1 and Revelation 19:13.  In verse 13 the word of God in the context is personalized by the pronoun "His" and "Him" and then in verse 14 He is then positively identified as our high priest, Jesus Christ. 

It is significant to note that the letter to the Hebrews was written many decades after the death, burial and resurrection of Christ.  Jesus' words reveal the will of God and are recorded for us in scripture. It is His words which are living and powerful and sharper than any two edged sword.  His words are what we have been left, recorded and preserved for us.  When we hold the scriptures in our hands, we hold the word of God.  This is the word that will be open at our judgment.  This is the word by which we will be judged.  Our eternal destinies rest on how we have handled and obeyed the word of God. 

Jesus Himself affirmed that His words were life in John 6:63, "It is the spirit that giveth life; the flesh profiteth nothing: the words that I have spoken unto you are spirit, and are life". 

Concerning the dividing of soul and spirit, think of the word spirit meaning the disposition of the individual. People can be mean spirited or good spirited which is an attitude or principle that inspires, animates, or pervades thought, feeling, or action. The word of God can divide a man's soul from his disposition and discern the thoughts and intents of the heart.

Rather than looking at the terms "soul" and "spirit" as two completely separate things, perhaps we should view this is an accumulation of terms meant to express the ability of God to penetrate and expose the inward mental nature of an individual.