Christian Liberty

[T]he consciences of believers, while seeking the assurance of their justification before God, must rise above the law, and think no more of obtaining justification by it. For while the law...leaves not one man righteous, we are either excluded from all hope of justification, or we must be loosed from the law, and so loosed as that no account at all shall be taken of works....

[L]aying aside all mention of the law, and all idea of works, we must in the matter of justification have recourse to the mercy of God only; turning away our regard from ourselves, we must look only to Christ. For the question is, not how we may be righteous, but how, though unworthy and unrighteous, we may be regarded as righteous. If consciences would obtain any assurance of this, they must give no place to the law.

Still it cannot be rightly inferred from this that believers have no need of the law. It ceases not to teach, exhort, and urge them to good, although it is not recognized by their consciences before the judgment-seat of God. The two things are very different, and should be well and carefully distinguished....

For when the conscience feels anxious as to how it may have the favor of God, as to the answer it could give, and the confidence it would feel, if brought to his judgment-seat, in such a case the requirements of the law are not to be brought forward, but Christ, who surpasses all the perfection of the law, is alone to be held forth for righteousness.

Source: John Calvin, Institutes of the Christian Religion, Bk 3, Ch. 19.