John 1:17 For the law was given by Moses, but grace and truth came by Jesus Christ.
The purpose of the Law of Moses (which includes the 10 commandments) was to REVEAL sin. It was never given as a means of salvation. The Apostle Paul describes it as a "schoolmaster":
Galatians 3:23 But before faith came, we were kept under the law, shut up unto the faith which should afterwards be revealed.
Galatians 3:24 Wherefore the law was our schoolmaster to bring us unto Christ, that we might be justified by faith.
Galatians 3:25 But after that faith is come, we are no longer under a schoolmaster.
The Law of Moses was TEMPORARY! God established the Law of Moses as a way of administering His ETERNAL moral absolutes through Moses...but Jesus Christ established grace as the NEW way of God's administering His moral absolutes. The Law of Moses had three aspects (civil, ceremonial, and moral) and it functioned as an indivisible unit. Therefore, when one places himself/herself under one aspect of the Mosaic Law, that person obligates oneself to be under the entire Law.
James 2:10 For whosoever shall keep the whole law, and yet offend in one point, he is guilty of all.
Galatians 3:10 For as many as are of the works of the law are under the curse: for it is written, Cursed is every one that continueth not in all things which are written in the book of the law to do them.
Galatians 3:11 But that no man is justified by the law in the sight of God, it is evident: for, The just shall live by faith.
Galatians 3:12 And the law is not of faith: but, The man that doeth them shall live in them.
Do you keep all 613 indivisible commandments of the Mosaic Law, HW? If not, you are guilty of breaking the whole law. Therefore, don't hypocritically judge others for not keeping the commandments when you know for a fact that you cannot "practice what you preach"! That is what the Pharisees were guilty of!
When Jesus died on the cross of Calvary and shed His precious blood, He redeemed us from the curse of the Mosaic Law and became a "curse" for us:
Galatians 3:13 Christ hath redeemed us from the curse of the law, being made a curse for us: for it is written, Cursed is every one that hangeth on a tree:
The NT Christian now serves God in in the "newness of the Sprit", not in the "oldness of the Mosaic Law...being "delivered" from its (the Law's) penalty:
Romans 6:14 For sin shall not have dominion over you: for ye are not under the law, but under grace.
Romans 6:15 What then? shall we sin, because we are not under the law, but under grace? God forbid.
"Thus, the Christian serves God in a sphere of administration of His absolutes which is different from the Mosaic Law" ...Renald E. Showers, There Really Is A Difference: A Comparison of Covenant and Dispensational Theology, pg. 191