Do not try to serve God under the old written code
In Romans 6:14 Paul makes one of the most counter-intuitive arguments in Scripture. He tells the members of the church in the imperial city of Rome, which included many Jews, that the reason why they were to stop living in injustice and lust was because they were no longer under the law, but under grace. A few paragraphs later, in Romans 7, he explains his reasoning.
Or do you not know, brothers – for I am speaking to those who know the law – that the law is binding on a person only as long as he lives? Thus a married woman is bound by law to her husband while he lives, but if her husband dies she is released from the law of marriage. Accordingly, she will be called an adulteress if she lives with another man while her husband is alive. But if her husband dies, she is free from that law, and if she marries another man she is not an adulteress.
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. For while we were living in the flesh our sinful passions, aroused by the law were at work in our members to bear fruit for death. But now we are released from the law, having died to that which held us captive, so that we serve not under the old written code but in the new life of the Spirit.
To be sure, we can still learn about what it means to walk in the Spirit and to live under grace by reading and studying “the old written code.” In fact, we should even be inspired by it. But as John Calvin said, it has no legal authority over us because we have already been declared to be in legal conformity to it as a result of the work of Jesus. Trying to serve God under the old written code is like pretending that Jesus never came, and it will always fail. But praise God that by his Spirit we now walk in love, fulfilling the law even as we are no longer bound by it.