“He only is my rock and my salvation, my fortress; I shall not be shaken. On God rests my salvation and my glory; my mighty rock, my refuge is God.”
Here is a battle-cry. It is the faith-filled boast of a saint embraced by gospel hope. What security rests behind our declaration of God as our rock, salvation, fortress, refuge? On what ground do we make such a boast in the midst of our uncertainties and darkness?
In a sermon entitled “Christ Crucified, Our Boast,” John Piper writes:
. . . [F]or the Christian, all boasting should be a boasting in the cross. All exultation should be exultation in the cross. If you exult in the hope of glory, let it be an exulting in the cross of Christ. If you exult in tribulation because tribulation works hope, let it be an exulting in the cross of Christ. If you exult in God, you are exulting in the cross of Christ. If you exult in your weaknesses, let it be an exulting in the cross of Christ.
Why is this the case? Because for redeemed sinners, every good thing — indeed every bad thing that God turns for good — was obtained for us by the cross of Christ.
Apart from the death of Christ, sinners get nothing but judgment. Apart from the cross of Christ, there is only condemnation. Therefore, everything that you enjoy in Christ — everything you boast in, everything you exult in — is owing to the death of Christ. And all your exultation in other things is to be an exultation in the cross where all your blessings were purchased for you at the cost of Christ’s life.