Christianity believes that the Church is now in a new covenant with God that began after the death and resurrection of Yeshua and the coming of the Holy Spirit. This new covenant replaces the old covenant that God gave Israel through Moses. The requirements of the new covenant are no longer the same since Yeshua fulfilled the law of Moses. Because of this, many Christians believe that the Old Testament is no longer binding. Others, however, believe that only the ritual laws could be set aside, while the moral laws are still in effect.
We find a description of the new covenant in Jeremiah.
Jeremiah 31:31-33 (KJV)
Behold, the days come, saith the LORD, that I will make a new covenant with the house of Israel, and with the house of Judah:
Not according to the covenant that I made with their fathers in the day that I took them by the hand to bring them out of the land of Egypt; which my covenant they brake, although I was an husband unto them, saith the LORD:
But this shall be the covenant that I will make with the house of Israel; After those days, saith the LORD, I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people.
On close examination we find that this new covenant is not with the Church, but rather with the house of Israel and the house of Judah. We also see from verse 33 that the law will continue to be in effect. The only difference is that the law would be written on the peoples' hearts. In other words by the coming of the Holy Spirit and His indwelling, the believer would be enabled to fulfill the law's requirements.
Despite the Scriptural evidence, many Christians will still believe that the Mosaic law is no longer applicable and that the covenant is not made with Israel. Yet, there is another evidence of the new covenant found in Deuteronomy.
Deuteronomy 30:1-8 (KJV)
And it shall come to pass, when all these things are come upon thee, the blessing and the curse, which I have set before thee, and thou shalt call them to mind among all the nations, whither the LORD thy God hath driven thee,
And shalt return unto the LORD thy God, and shalt obey his voice according to all that I command thee this day, thou and thy children, with all thine heart, and with all thy soul;
That then the LORD thy God will turn thy captivity, and have compassion upon thee, and will return and gather thee from all the nations, whither the LORD thy God hath scattered thee.
If any of thine be driven out unto the outmost parts of heaven, from thence will the LORD thy God gather thee, and from thence will he fetch thee:
And the LORD thy God will bring thee into the land which thy fathers possessed, and thou shalt possess it; and he will do thee good, and multiply thee above thy fathers.
And the LORD thy God will circumcise thine heart, and the heart of thy seed, to love the LORD thy God with all thine heart, and with all thy soul, that thou mayest live.
And the LORD thy God will put all these curses upon thine enemies, and on them that hate thee, which persecuted thee.
And thou shalt return and obey the voice of the LORD, and do all his commandments which I command thee this day.
This passage took place as the Israelites were about to enter the promised land. God had just outlined blessings and curses that would result based on the peoples' faithfulness to God's covenant commands. From history we know that Israel was often very faithless and suffered under the curses that God said would result. However, from this passage we see that at some future time Israel will turn again to the Lord wholly (verse 2) and God would gather His people from all the nations where they had been exiled. He would have compassion on them and would bring them back to the land of Israel (verses 3-5). God would circumcise their hearts (verse 6) and would place all the curses on the enemies of His people (verse 7). Through this the people of Israel would return to God, obey His voice, and OBEY all His commandments that God had commanded them that day (verse 8).
This prophecy of Moses did not occur during the days of Moses, but rather is now only beginning to take place as we see the Jews returning to Israel. Although it is true now, that as believers, we have the Holy Spirit and His enablement, the Jews are, as a nation, only beginning to return to God. Their full salvation is yet a future event. But this is a description of the new covenant. Being circumcised in the heart is another way of speaking about the Holy Spirit's work in the believer. When the Jews return to God, their circumcision of heart will allow them to obey God. What commandments are they going to obey? Those that Moses had spoken to them (verse 8).
So if the new covenant is between God and Israel (with Judah, making the two houses complete) how can believers participate? When we are saved we are grafted into Israel. Israel's future becomes ours. If Israel will be required to follow the law of Moses (actually the law of God) so will the believers.
There is also Scriptural evidence that points to God never annulling prior covenants.
Galatians 3:17 (KJV)
And this I say, that the covenant, that was confirmed before of God in Christ, the law, which was four hundred and thirty years after, cannot disannul, that it should make the promise of none effect.
What Paul was saying in Galatians is that any promises that God has made, He will fulfill. The Mosaic law, which came after the Abrahamic covenant by 430 years could not annul the Abrahamic covenant. In like manner, the promises made to Israel in the Mosaic (or Old) covenant cannot be annulled by any future covenant.
Since the only covenants that God has made have been between God and Israel, with Gentile believers coming in by grafting, there is no other covenant that allows any believers, Jew or Gentile, to ignore the commands written in the Old Testament.
The new covenant isn't really so new after all.