Right here we have one more difference between the Law and the Gospel. The Law does not bring on the Holy Ghost. The Gospel, however, brings on the gift of the Holy Ghost, because it is the nature of the Gospel to convey good gifts. The Law and the Gospel are contrary ideas. They have contrary functions and purposes. To endow the Law with any capacity to produce righteousness is to plagiarize the Gospel. The Gospel brings donations. It pleads for open hands to take what is being offered. The Law has nothing to give. It demands, and its demands are impossible.
Martin Luther, Galatians Commentary
Law, Grace, & Daily Living 