Do we then overthrow the law by this faith? By no means! On the contrary, we uphold the law.
A lot of people think faith is the opposite of law. The basic notion here is that the God of the Old Testament Who gave the law is mean and that the God of the New Testament is nice. The problem is: there aren't two Gods, just one. The God Who gave the law in the Old Testament is the God Who, through Jesus Christ, makes it possible to keep the law in the New Testament. For the revelation in which we have faith is that Love has become man, died, and risen from death so that we might be filled with the Holy Spirit of love, which is the fulfilment of the law.