Many Christians divide the law of Moses into different parts – usually the divisions are moral, civil, and ceremonial. The concept of dividing it up is not from anything we get out of the Scriptures however, which is important to bear in mind. The Bible always speaks of the law (Torah, commandments of Moses) as a whole, never in parts or divisions, some pertinent and some not.
When the law of Moses was given, the Lord established it as part of the Mosaic covenant He made with the people of Israel. The laws were the terms of the covenant – a covenant which was unequivocally eternal and which God was never going to revoke. For the Mosaic legislation to be ‘done away with’ that would mean the Mosaic covenant would need to be done away with – an impossibility because God is a covenant-keeper and He vowed to always uphold this covenant with Israel.
The New Covenant, introduced in Jeremiah 31:31-33 God describes as 1) being with the house of Israel and the house of Judah and 2) it involves putting His law within them and writing it on their hearts. This is why Messianic believers often refer to the New Covenant as the Renewed Covenant because it consists not of new laws and new terms but the ‘old’ law made new and God’s people empowered to actually live it. In Matthew 5:17 Jesus says that He did not come to abolish the Law or the Prophets but to fulfill them. Many Christians understand Jesus fulfilling the commandments as doing away with them so we don’t have to obey them anymore. This however, is incongruous with the context of the passage as well as the rest of Scripture. In later passages of Scripture Christians are exhorted to fulfill (do) the law, following in Christ’s footsteps.
As believers in Jesus, we are grafted into the ‘commonwealth of Israel’ and become part of God’s family and people Israel (Ephesians 2:12-14). Thus we become a part of and connected to God’s covenant and His covenant people. We are part of Israel and thus become partakers of the New Covenant, the law of God written on our hearts.
Therefore, I believe that the commandments in the Old Testament are just as important to follow as we follow Jesus as the commandments in the New Testament and as we pursue righteousness we should seek to conform our lives to all the commands in Scripture. Granted, many of the commandments are inapplicable to me personally (laws for the army, high priests, etc) and many we are unable to do because we are not in the land of Israel, there is no temple, altar, priesthood, or Sanhedrin (Court of Torah law). However, it is still God’s standard of righteous living and there are blessings in keeping the law of God as we seek Him out of love and desire, not to gain His favor, forgiveness, or righteousness.