Choose Christ
or the Law

Because...folk mix Law and Gospel, they can only be subverters of the Gospel; for either Christ will stand and the Law will fall, or the Law will stand and Christ will fall. For Christ and the Law agree in no wise and cannot dwell in a conscience at the same time. Where the righteousness of the Law reigns, there the righteousness of grace cannot reign; and, on the other hand, where the righteousness of grace reigns, there the righteousness of the Law cannot reign.  The one must give way to the other. But if you cannot believe that God, for the sake of Christ, whom He sent into the world to become our High Priest, wants to forgive sins, how, I ask you, could you believe that He will forgive them for the sake of works of the Law, which you have never performed, or for the sake of your works, which, as you must confess, are such that it is impossible to confront the judgment of God with them. 

Source: Quoted in Ewald M. Plass, What Luther Says, A Practical In-home Theology for the Active Christian.  St. Louis: Concordia Publishing House.  1959 Edition, 10th Printing (1994), p. 339.