Romans six teaches us: those of us who have placed our faith in Christ, and his work on the cross, are to reckon ourselves dead to sin. You see, just as all were originally born in Adam and are therefore sinners, those of us who have been born again have been born into Christ and made righteous. In other words, the cross is the means by which God transfers us from the first Adam to the last.
Human beings have never been independent we have always been in union with another spirit. For instance we are either a slave to sin or a slave to righteousness. Notice we are always a slave and never our own master. The good news is in Christ our old boss is out and our new one is in. This is what Paul means with his frequent use of the term “Christ in you” and “In Christ.”
As we move from Romans six into Romans seven we read about a wife who simply cannot please her husband and needs to be separated from him, but the law won’t allow it. You see unless he dies, she has to remain married to him and the truth is he simply will not die. This is a picture of our relationship with the Law/sin meaning the Law isn’t going to die, and it is the means by which sin gets its power, so she/we are in a quandary. How will she/we get away from her old husband if he won’t die? God has a solution.
You see God has always known the husband wouldn’t, die but His plan involves the wife/us dying instead. If God crucifies us with Christ and raised us back up with him there would be legal grounds for divorce from the old husband, and we could then be joined to a new one, namely Christ himself. That’s exactly what He did.
The reason Paul uses a wife here as an illustration is because God is looking to produce fruit through His people but like a wife we have to have Him to do it. Just as a wife needs a husband to produce children we too have to have God in order to produce fruit for God. This analogy is teaching us that there is absolutely no way for us to produce fruit for God by way of the Law. Us attempting to produce fruit for God by the Law is the same as a wife trying to have a baby without her husband. It just simply cannot happen. The fruit bearing process requires the husband. Just as a wife has to become one flesh with her husband we must be one spirit with the Lord.
Essentially Romans six and the first part of seven is telling us we have died to sin by being severed from our union in Adam. Through the cross, and our being co-crucified, dead, buried and risen with Christ we walk in newness of life we are now in union with Christ, so He can now produce His fruit through our lives.