The Ten Commandments are not totally relevant to Christian life. The reason is that they were the heart of the covenant between God and Israel. The Bible explains why the Ten Commandments were given.
Then Moses went up to God, and the LORD called to him from the mountain and said, "This is what you are to say to the house of Jacob and what you are to tell the people of Israel: 'You yourselves have seen what I did to Egypt, and how I carried you on eagles' wings and brought you to myself. Now if you obey me fully and keep my covenant, then out of all nations you will be my treasured possession. Although the whole earth is mine, you will be for me a kingdom of priests and a holy nation.' These are the words you are to speak to the Israelites (Ex 19:3-6).
The LORD our God made a covenant with us at Horeb. It was not with our fathers that the LORD made this covenant, but with us, with all of us who are alive here today. The LORD spoke to you face to face out of the fire on the mountain (Deut 5:2-4).
These are the commandments the LORD proclaimed in a loud voice to your whole assembly there on the mountain from out of the fire, the cloud and the deep darkness; and he added nothing more. Then he wrote them on two stone tablets and gave them to me…..So be careful to do what the LORD your God has commanded you; do not turn aside to the right or to the left. Walk in all the way that the LORD your God has commanded you, so that you may live and prosper and prolong your days in the land that you will possess (Deut 5:22,32-33).
The Ten Commandments were the expression of the covenant between God and the children of Israel. To keep their side of the covenant, Israel was required to keep all Ten Commandments. Most of the commandments had penalties for disobedience. This covenant with God was enforced by the civil authorities through the justice system. Under this system, blasphemy was a crime punishable by the civil authorities.