Goliath's sword and the Cross

Today I was reading a Puritan prayer about the sin that lurks inside us.

Destroy, O God, the dark guest within
whose hidden presence makes my life a hell.
Yet thou hast not left me here without grace;
The cross still stands and meets my needs
in the deepest straits of the soul.
I thank thee that my remembrance of it
is like David's sight of Goliath's sword
which preached forth thy deliverance.

I had never thought to compare the Cross to Goliath's sword. Both were instruments of the enemy- a Roman cross and a Philistine weapon. Both were used triumphantly to bring victory to hopeless people. Looking at the cross should make us tremble in terror and shame that the Son of God would die that way, but it should also make us utterly grateful that His redemptive grace is extended to us!