Why do the laws of Moses no longer apply to Christians? Are they not also the Word of God?

Luther:

That is right, but you have to see who they are addressed to. Suppose that a family man says to his manservant that he has to plough an acre and to his wife that she has to work in the kitchen. And suppose that the wife went ploughing the acre and that the manservant went working in the kitchen and that they both say: ‘It is an order of the family father!’ Than the father would take a club and say: It was my order, but not for you. Everybody has his own order and you have to it. So the laws of Moses are not for the pagans, but only for the Jews. That even goes for the Ten Commandments, because God Himself says: ‘I am the LORD thy God, Which hath brought thee out of the land of Egypt, out of the house of bondage’, and He did not bring us, but only the Jews out of Egypt. And Moses commanded in the fourth commandment observance of the Sabbath, but Paul and the New Testament abolished the Sabbath, so that it is abundantly clear that the Sabbath was only given to the Jews. When I want to abide by Moses in one commandment, then I have to become a Jew and accept the whole Law of Moses (Galatians 5:3).