The differentiating quality of faith is that the nature and function of faith is to rest completely upon another. It is this resting, confiding, entrusting quality of faith that makes it appropriate to and indeed exhibitive of the nature of justification. It is consonant with its source as the free grace of God, with its nature as a forensic act, and with its ground as the righteousness of Christ. Faith terminates upon Christ and his righteousness and it makes mention of his righteousness and of his only. This is the Savior’s specific identity in the matter of justification-he is the Lord our righteousness. And in resting upon him alone for salvation it is faith that perfectly dovetails justification in him and in his righteousness. Other graces or fruits of the Spirit have their own specific functions in the application of redemption, but only faith has as its specific quality the receiving and resting of self-abandonment and totality of self-commitment.
This is both the stumbling-block and the irresistible appeal of the gospel. It is the stumbling-block to self-righteousness and self-righteousness is the arch-demon of antithesis to grace. It is the glory of the gospel for the contrite and brokenhearted-if we put any other exercise of the human spirit in the place of faith, then we cut the throat of the only confidence a sinner conscious of his lost and helpless condition can entertain. Justification by faith is the jubilee trumpet of the gospel because it proclaims the gospel to the poor and destitute whose only door of hope is to roll themselves in total helplessness upon the grace and power and righteousness of the Redeemer of the lost. In the words of one, ‘cast out your anchor into the ocean of the Redeemer’s merits’.
Collected Writings of John Murray – Volume 2: Systematic Theology (Edinburgh, Scotland: The Banner of Truth Trust, 2009), 216-217.