The Logos of God Guarantees Our Entrance Into Eternal Rest

What is the Word of God in Hebrews 4:12? It is Jesus? It is Scripture? The parallelism in the passage presents a dualistic meaning on so many levels giving the culminating in verse 12. This begins with the author of scripture David vs. God. Then it moves to the rest vs. the Rest. Then Joshua vs. Jesus or Jesus vs. Joshua. Finally, the author points to the Word of God (as in the promise of God) vs. the Word of God (as in the Son of God) in a very subtle way.