what did Christ becoming the curse under God accomplish for us?
Christ became the curse under God and fulfilled all the curse of the Law, accomplishing forgiveness, reconciliation, and pardon for every human being who has ever lived. This provision is available to anyone and everyone who will simply believe it, not by keeping the Law.
Les teaches that the horrible, worst imaginable sins of the human race were all laid on Christ. He took the place of that rebel, sinful son of Israel so that God could put the curse of the Law on Christ. Christ became the curse under God and fulfilled all the curse of the Law. This accomplished God's declaration of forgiveness, reconciliation, and pardon for every human being that has ever lived. That provision is there for anyone and everyone who will simply believe it, though many refuse to believe. Les also connects this to Romans 3, where the plan of salvation from Paul's pen begins and where keeping the Law provides no justification.