The word curse means to be cut off, that is cut off from the blessing of God and marked for destruction. God's covenant of law promised blessings to those who obey and curses to those who disobey (Deuteronomy 28:15-24). The curse of sin cuts us off from the blessings of God.
Martin Luther taught that Christ died for the curse of our sins. "He voluntarily fulfilled all righteousness, living under the law without spot or blemish, bore our sins, became a curse for us, and offered himself as a sacrifice for the sins of the world. This is the atoning, reconciling work of Christ."
Man living in sin is controlled by a spirit of disobedience (Ephesians 2:1-3). He is under the dominion of sin and the curse of the law. His only hope of salvation is in the sacrifice of Christ alone. As Luther said, Christ "became a curse for us, and offered himself as a sacrifice for the sins of the world."
The curse of sin is removed by faith in Christ as our sacrifice! Luther taught that Christ in the atonement "became a curse for us" at the cross (Gal. 3:13). He wrote, "This is the atoning, reconciling work of Christ." That means by grace through faith in the atonement of Christ, we are free from the curse!