Taken from Covenant and Salvation: Union With Christ in the chapter entitled”Mystical Union in Reformed Soteriology” by Michael Horton, page 151.
“Due to sin, the law as a covenant of life simply makes one more deeply egocentric. In Paul’s understanding “boasting” in one’s own righteousness, far from unseating the reign of sinful autonomy, is the throne from which the autonomous self spreads it dominion. However, when its real intentions and demands are announced, the law begins to break up this autonomy at its heart by exposing our delusions of grandeur and stability, allowing the gospel to do its work of taking us entirely outside of ourselves and locating existence in Christ alone. In this sense the law in its wrath even serves as a merciful accomplice to the Gospel:
For through the law I died to the law, so that I might live to God. I have been crucified with Christ; and it is no longer I who live, but Christ who lives in me. And the life I now live in the flesh I live by faith in the Son of God, who loved me and gave himself for me. I do not nullify the grace of God, for if righteousness were through the law, then Christ died for no purpose. (Gal. 2:19-21)”
Get this book. Check it out at your library (request it) or buy it. It is well worth it!