According to the marriage analogy inserted into this text in verses 2 and 3, the husband has to die before the wife is free to marry another husband. Using that example, verse 4 redefines the terms that the author presented so that it applies our relationship with the law and with Jesus Christ:
Therefore, my brethren, you also have become dead to the law through the body of Christ, that you may be married to another----to Him who was raised from the dead, that we should bear fruit to God.
The marriage analogy is presented first, and then the application of the analogy is given in the tenor of "likewise...". The first husband was the law, from which we need to be separated from before we can become married to another, Who is Jesus Christ.
The first half of Romans 7 is prefaced with the qualification "
for I speak to those who know the law", and the narrative you're having so much trouble with is sandwiched between these two antithetical points made by the author:
- the law has dominion over a man as long as he lives - 7:1
- But now we have been delivered from the law, having died to what we were held by - 7:6
The example of marriage was inserted between these to help lead the reader into the realization that one is bound (held, under dominion) to either the law or to Jesus Christ. It is not possible to belong to both, and redemption from the ownership of the law is a common theme most sabbatarians don't have a grasp of.
Instead of following the flow of a narrative written by the author, you jump ahead and practice the same method of "line upon line, precept upon precept" that Isaiah 28:13 warns us to be a eisegetical trap and snare. No doubt that's why you grasp at baptism, which is foreign to Romans 7.