Do Christians need to adhere to the laws of the Old Testament?

Do Christians need to adhere to the laws of the Old Testament?
The people of the Old Testament proved our need for a savior. They were held to laws about sacrificing animals to purify them of their sins, laws about food preparation and consumption, laws about righteous living, and laws about a host of other topics. A person had to work daily to keep clean and worthy of God's mercy. God's desire has always been to redeem the lost. But, before He could do that, He needed to prove that man was unable to create his own worthiness in the face of God's holiness. The Bible stresses, "Clearly no one is justified before God by the law, because, 'The righteous will live by faith'" (Gal. 3:11). God's perfect plan was to let man flounder for a while as he tried to earn God's favor. Then, when the situation proved hopeless, God came as the Messiah to be the final, pure sacrifice for the sins of man.
Jesus Christ fulfilled the Law, which required a blood sacrifice for the remission of sins. "In fact, the law requires that nearly everything be cleansed with blood, and without the shedding of blood there is no forgiveness" (Heb. 9:22). And, Ephesians 1:7 says, "In him we have redemption through his blood, the forgiveness of sins, in accordance with the riches of God's grace that he lavished on us with all wisdom and understanding." Jesus was the final, pure, spotless lamb, sacrificed as payment for the sins of man, that we might have everlasting life. The New Testament is our covenant with God under the blood of Christ. In it, we are instructed about living a moral lifestyle and serving others so that they may know God. Galatians 5:14 says, "The entire law is summed up in a single command: Love your neighbor as yourself."
A further point is necessary: Many people, even entire denominations, build their faith around their acts of service and good deeds. Not only does this fail to earn them entrance into God's Kingdom--only salvation through the blood of Christ can do that--but it tramples all over the cross of Christ. If mankind were able to earn God's favor, He would have let us do just that--instead of sending His only Son to die. If we continue to live as though we have something of worth and can earn God's favor, then we are denying the powerful and complete work of the cross.