John Murray wrote, "This also Paul states explicitly, 'But if we died with Christ, we believe that we shall also live with him, knowing that Christ being raised from the dead dies no more, death has no more dominion over him" (Romans 6:8-9). Just as Christ died and rose again, so all who died in him rose again with him."
Christ not only died for us, but according to Scripture, all believers died in him and rose again from the dead in him. God sees all true believers as one body in Christ. Our corporate identity is who we are in Christ.
Adam was the representative of mankind in sin and death. Therefore, we are all born with a sin nature and appointed unto death. Christ is every believer's representative in his death and resurrection. We died in Christ. We are risen in Christ. Because he lives forever in a glorified body, we shall be glorified together in him with life eternal.
Baptism displays our corporate identity as believers in Christ. "Therefore we were buried with him through baptism into death, in order that as Christ was raised from the dead through the glory of the Father, even so we should walk in newness of life" (Romans 6:4). The apostle Paul concludes, "For you died, and your life is hid with Christ in God" (Colossians 3:3).