Heb. 8:7 For if that first covenant had been faultless, there would have been no occasion to look for a second.
Hebrews 8:13 In speaking of a new covenant, he makes the first one obsolete. And what is becoming obsolete and growing old is ready to vanish away.
John 1:17 For the law was given through Moses; grace and truth came through Jesus Christ.
Matthew 22:37-39 And he said to him, "You shall love the Lord your God with all your heart and with all your soul and with all your mind. 38This is the great and first commandment. 39And a second is like it: You shall love your neighbor as yourself.
The law kills, does not save, and as part of the covenant given to Moses is now obsolete. Grace and truth came through Jesus Christ who guarantees this better and saving covenant. The old covenant depended on mechanical external law keeping that flowed from duty. The New Covenant believer is given a regenerated heart by God's grace and a new attitude that has been wrought by the Holy Spirit.
Paul warns in Galatians that attempts to satisfy the demands of the law out of duty and to be righteous are futile (Galatians 2:16). Jesus Christ perfectly obeyed the law and died on the cross to pay the penalty for the sins of all that place their faith and trust in him and his righteousness. This saving faith gains access to an alien righteousness that is imputed to all that trust him. We are justified before God by the work of Christ and not our own works.
I am in no way suggesting that Christians should ignore sanctification and Christian living. However, grace and truth came through Jesus and believers are led by the Spirit and are enabled by the Spirit to follow and obey Jesus and his teachings. This is a dependence on grace rather than external law keeping. Jesus says that the law can be summed up by the greatest commandment which is “You shall love the Lord your God with all your heart and with all your soul and with all your mind.” He also said, “if you love me, you will obey my commands.” Notice Jesus does not say, “if you love me, you SHOULD obey my commands.” No, he says you WILL. This is grace and it comes with power. It does not make a redeemed sinner perfect, but unlike the law, it does not have to make sinners perfect because Jesus paid it all and all to him I owe as the great ole hymn proclaims.
Praise God that the New Covenant replaced law keeping with grace and truth. Let us as Christian keep our eyes on Jesus and his grace and not become entangled with Moses and the law. Jesus saves and the law kills.