The Grace Reading
Paul argues from a rule his readers already accept. A wife is legally bound to her husband while he lives and free the moment he dies. Nothing else dissolves that bond. Not distance, not sincerity, not a quiet decision to stop trying. Only a death.
Then comes the turn, and it is not the one you expect. Paul does not say the law died. He says “you also have become dead to the law through the body of Christ.” The funeral was yours. It happened in His body, at His cross, long before you had an opinion about it. You were carried out of the first marriage by a death and into the second by a wedding, and both of them happened on the same hill.
Look honestly at that first marriage. Paul will call the law holy and just and good a few verses later, so the problem was never the husband's character. The problem was the fruit. “The sinful passions which were aroused by the law were at work in our members to bear fruit to death.” That household produced obligation, comparison, and exhaustion. It could tell you what was right with perfect accuracy. It could not make you fruitful.
The second marriage arrives with a purpose clause attached: “that you may be married to another—to Him who was raised from the dead, that we should bear fruit to God.” Fruit is what a union produces. It is never what a contract extracts. A branch does not strain to manufacture grapes; it stays attached (John 15:5). Whatever grows in this marriage grows out of who you are joined to.
Which is why verse 6 can say “we should serve in the newness of the Spirit and not in the oldness of the letter” without a trace of anxiety in it. Serving did not stop. Its source changed. The letter demanded obedience and got very little of it. The Spirit draws it out of union, and that difference is the whole of the New Covenant in one sentence.
You are not on probation in this marriage. The Husband you were joined to was raised from the dead, and “death no longer has dominion over Him” (Romans 6:9). The bond holds because He holds it, and He is not going anywhere.
The Common Misreading
The passage gets flattened in two directions. Some hear pure permission and conclude nothing at all is asked of a Christian, which misses that verse 6 ends in service. Others agree in principle that we died to the law and then hand the reader a fresh list of requirements, so the widow simply remarries the same husband under a Christian name.
A widow is not set free in order to belong to no one. She is set free in order to belong to someone else. That is the entire force of the analogy. You are joined, deeply and permanently, and everything Paul expects of you grows out of that union rather than being pried out of you by a rule.