for the sake of troubled hearts

In order, therefore, that troubled hearts may have a firm, sure consolation, also, that due honor be given to the merit of Christ and the grace of God, the Scriptures teach that the righteousness of faith before God consists alone in the gracious [gratuitous] reconciliation or the forgiveness of sins, which is presented to us out of pure grace, for the sake of the only merit of the Mediator, Christ, and is received through faith alone in the promise of the Gospel. In like manner, too, in justification before God faith relies neither upon contrition nor upon love or other virtues, but upon Christ alone, and in Him upon His complete obedience by which He has fulfilled the Law for us, which [obedience] is imputed to believers for righteousness.
Solid Declaration, FC 1580