Galations 5: What law?
In this book, Paul is getting on the Galation's case because they became diverted from the gospel. Some people came to them teaching that it was necessary to follow Old Testament rules of the law in addition to the gospel.
For humans, the goal of things spiritual is to connect them with the divine. For Christians, that means getting into a right relationship with God. However, the Old Testament law didn't perform this function at all. In fact the purpose of that law was to make people aware of how much they were unlike God (Rom 7:7). Paul confirmed that the law the Galations had returned to had failed them when he said: "If you keep on biting and devouring each other, watch out or you will be destroyed by each other." (Gal 5:15)
If the Old Testament law had worked to make right relationships, everybody would instinctively know it. It would not have been necessary for Jesus to bring the gospel to us. The important thing to realize is that God didn't bring us something to complete the law, but to replace the law. We can see this because Paul says "The entire law is summed up in a single command: "Love your neighbor as yourself." (Gal 5:14)
But love is not something that can be commanded! The law is powerless to make this happen. Love is something that comes from the heart: only from a heart changed to be like God's. The gospel that Jesus brought us can change the heart to love, therefore there is no need to observe the OT law because it will already have been fulfilled.
Paul said: "The only thing that counts is faith expressing itself through love." (Gal 5:6) This statement is critical to understand because it connects the two parts of the gospel: - the part we believe and the part we do. * The gospel is a complete solution to God and to good relationships.