Romans 5:21 : "That, as sin reigned in death, even so might grace reign through righteousness unto eternal life through Jesus Christ our Lord." Sin caused death, but that is not what Paul here has in mind. Sin reigned in death--in the sphere or realm of death. That Paul is here referring to spiritual life and spiritual death is made clear by the verses that immediately follow in the next chapter. In spiritual death sin's reign is absolute; it is the reigning monarch in every man who is dead in sins. But grace reigns through righteousness--that is, through this gospel plan of righteousness. It is God's grace that produced this plan of righteousness it is the power that banishes sin from the heart and leads a man in devoted service to God. The ultimate result of its reign is eternal life through Jesus Christ our Lord.