What must a fallen creature do to be brought back to his original state?
A fallen creature is restored to his original state by faith, not by personal merit or works. God has already done everything necessary through Jesus Christ, who paid the debt and made reconciliation possible. The required response is simply to believe, trusting what God has provided, for restoration has always come by faith.
Les explains that Adam was created innocent, sinless, and perfect, but Adam fell, and God decreed that everyone coming from Adam would be a fallen creature. People are not condemned because they personally ate forbidden fruit; they inherited that condition as sons of Adam and are born spiritually dead and alienated from God. Yet God did everything needed to bring that fallen creature back to his original state, if they would simply believe. Restoration has always been by faith—Adam and Eve were restored into fellowship by faith, and the Old Testament saints likewise. Through Jesus Christ, God superseded Adam's ruin, reconciled the human race, paid the debt, and made everything possible to bring men back to Himself.