(6:2-7)How can we who died to sin still live in it? Do you not know that all of us who have been baptized into Christ Jesus were baptized into his death? We were buried therefore with him by baptism into death, in order that, just as Christ was raised form the dead by the glory of the Father, we too might walk in newness of life.
For, if we have been united with him in a death like his, we shall certainly be united with him in a resurrection like his. We know that our old self was crucified with him in order that the body of sin might be brought to nothing, so that we would no longer be enslaved to sin. For one who has died has been set free from sin.
Likewise, my brothers, you also have died to the law through the body of Christ, so that you may belong to another, to him who has been raised from the dead, in order that we may bear fruit for God. [...] Now we are released from the law, having died to that which held us captive.(7:4,6)
Now, those who know me know that I am still living in the same physical body I have had since I was born. So what does Paul mean that I, as a Christian, have died or even been crucified?
Well, it revolves around the concept called the Substitutionary Atonement of Christ, meaning that Christ died as our substitute: we, as sinful humans, deserved death but Christ died instead—and, even more, Christ deserved life but we sinful humans got life instead!
Now I would say most Christians understand Substitutionary Atonement at this basic level but, paying attention to Paul's wording here, he is taking the concept deeper. My old self—before I became a Christian—was sinful and did not care for God or His law. This self deserved condemnation and punishment. And now, when God looks at me, does He say, "that is one sinful man, but each of those sins was paid for by Jesus, so he owes me nothing?" No. What Paul is saying is that in God's eyes, God killed that man when He killed Jesus. (Yes, it was ultimately God, not Jews or Romans, who killed Jesus. "Yet it was the will of the Lord to crush him" (Isaiah 53:10). Amazing love!) Let me say again: in God's eyes, my old self is dead. Not only were my sins punished in Jesus' death, but my old man was punished—with death, as required by the law.
And thus the symbol of baptism: our old self enters the water and is "buried with him [...] into death" (6:4) and our new man rises from the water "in a resurrection like his" (6:5). And thus, as well, why Paul is so adamant that the Christian must not sin: it is utterly incompatible with the life we live. I must not say, "well, that was wrong, but it was just one more sin Jesus had to pay for," but instead, "I am a new man now. The old man was the sinner, but this new man is to walk in newness of life."
Now this isn't a brand new truth to me and may not be to you either, but I was quite encouraged as I read and dwelt on this doctrine this morning so I wanted to write about it: mostly for my sake but by hopefully for yours as well. If you are reading this as a Christian, you are raised from the dead! And that is not a metaphor: that is actually how God sees you. So walk in newness of life!