Let us therefore be diligent to enter that rest, lest anyone fall according to the same example of disobedience.
For the word of God is living and powerful, and sharper than any two-edged sword, piercing even to the division of soul and spirit and of joints and marrow, and is a discerner of the thoughts and intents of the heart.
And there is no creature hidden from his sight, but all things are naked and open to the eyes of Him to whom we must give account.
Seeing then that we have had a great High Priest who has passed through the heavens, Jesus the Son of God, let us hold fast our confession.
For we do not have a High Priest who cannot sympathize with our weaknesses, but was in all points tempted as we are, yet without sin.
Let us therefore come boldly to the throne of grace, that we may obtain mercy and find grace to help in time of need.
The "same example of disobedience" is that spoken of earlier of the Israelites who did not trust God's promises but instead, through lack of faith, were sent to spend forty more years in the wilderness. Paul admonishes us to be diligent in practicing our faith that we not fall according to this old example.
And then he gives this complex description of Christ, the Word of God, through a series of striking and terrifying metaphors. Christ is a double-edged sword that pierces even between our spirit and soul (what exactly is that division?) and discerns our true intents.
(In the Greek New Testament, the phrase "λογος του θεου" ('logos tou Theou' or 'word of God') is a name for Christ; Scripture is referred to not as "λογος" but as " Γραφή" ('Graphi' or 'Writings')
And yet Christ the piercing sword is also our High Priest who will be faithful to save us, having been tempted in all the ways that we are and having yet resisted sin in all. He knows the path we're on, and he knows how to walk it safely. So the passage ends with another admonition-- yes, we must be careful and diligent, because Christ knows our deepest thoughts. But we also must be bold, because Christ is full of mercy and grace.