Justification by faith not only carries with it many benefits ( Romans 5:1-11), but it also overcomes the effects of the Fall. Paul"s final argument in support of justification by faith involves a development of his previous emphasis on the solidarity that the saved experience with their Savior ( Romans 5:1-2; Romans 5:9-10). In this section ( Romans 5:12-21) he expanded that idea by showing that just as Adam"s sin has affected all people, so Jesus Christ"s obedience has affected all believers. [source][source][source]
"As Adam"s one sin never fails to bring death, so Christ"s one righteous act in behalf of sinners never fails to bring the opposite award to those who are in Him." [1][source]
The apostle viewed Adam and Christ as federal heads of two groups of people. A federal head is a person who acts as the representative of many others and whose actions result in consequences that the individuals he represents inevitably experience. Some interpreters believe Paul viewed Adam as the natural head of the human race, rather than as the federal head. [2] Examples of federal heads include a king, a president, a member of congress, and a parent, among others. [source][source][source]
In this section Paul was not looking primarily at what individual sinners have done, which had been his interest previously. Rather he looked at what Adam did in the Fall and what Jesus Christ did at the Cross and the consequences of their actions for humanity. Adam"s act resulted in his descendants sinning and dying. We inherit Adam"s nature that was sinful, and this accounts for the fact that we all sin and die. We are sinners not only because we commit acts of sin but also because Adam"s sin corrupted the human race and made sin and punishment inevitable for his descendants as well as for himself. However, Christ"s act of dying made all who trust in Him righteous apart from their own works. [source][source][source]
"When one man fails in the accomplishment of God"s purpose (as, in measure, all did), God raises up another to take his place-Joshua to replace Moses, David to replace Saul, Elisha to replace Elijah [3]." [4][source]
"The power of Christ"s act of obedience to overcome Adam"s act of disobedience is the great theme of this paragraph.... [source][source][source]
"The main connection is with the teaching of assurance of final salvation in the immediately preceding paragraph ( Romans 5:2 b, 9-10). The passage shows why those who have been justified and reconciled can be so certain that they will be saved from wrath and share in "the glory of God": it is because Christ"s act of obedience ensures eternal life for all those who are "in Christ."" [5][source]