Overview: A key tenet of Christianity is the belief that most of the biblical laws are void from the time of Jesus’ passing and on. These laws were coined the “Mosaic Laws.” What does Scripture say about the eternity of Mitzvos and whether they still apply today?
There are three general opinions regarding the view of the New Testament on the question of whether or not Jews are to keep all the Mosaic (i.e. Old Testament) commandments: (1) They are not to do so. This is the opinion of most Jewish missionaries who say that that there are two salvation methods: There’s the Mosaic kind which only works if the Law is entirely kept with zero sin whatsoever, and then there’s believing in Jesus.[i] (2) They are exempt but it’s permissible. (3) They are required.[ii]
The third opinion seems to be rejected by the New Testament in which Paul (a Jew) declares himself free of Mosaic Law. We will now proceed to present evidence from Scripture that unequivocally proves that the Mosaic Law was intended to last through the ages until the present. Consequently, a key New Testament doctrine will be flattened. Alternatively (if one holds of the third opinion brought in the previous paragraph despite its issues), the New Testament will prove to be irrelevant to the Jew as he is still bound (i.e. privileged) to the eternal Mosaic Law.
Great skepticism should be applied to a belief that has come to make lenient and easier. Judaism is complex with many details and the righteous are only righteous through their actions, while belief alone is of no righteousness of its own. Judaism, when properly kept with its highest standards, is arguably the world’s hardest religion as it accompanies every step of our daily actions. Christianity then comes and makes things easier with a new “Bible” (i.e. the New Testament) and a new “Israel” (i.e. faithful Christians).
Great suspicion arises that Paul developed his beliefs not from divine Revelation and truth, but for a means to attract the crowds and the masses to his religion by making the observance easier. By claiming righteousness with no actions but mere “belief in the heart”—one believes they have the best of both worlds, both an easy lazy life, with few actions needed, and eternity in the World to Come (earned by a simple “belief”).
Obviously, this on its own doesn’t invalidate the claim at its start, but it’s definitely a good starting point and a valid reason to have great suspicion regarding the authenticity of the Christian movement.
Christianity abandons most of the “Mosaic Commandments” (definitely for Gentiles) while in return requires belief for Jesus in the heart. They say that the belief is actually a completeness of the commandments to its fullest and thus substitutes it. Well, I must object for multiple reasons:
First of all, I wonder how “belief” is a substitute for the Mitzvos that entail actions unrelated to morality and faith; for example the prohibition against eating pork.[iii] It’s merely a play of words to call it a “substitute.” Secondly, all over the Torah (specifically in Deuteronomy) it mentions over and over “to do…” regarding all the commandments, indicating an action.
Some missionaries will respond to this by saying that the Mitzvos weren’t intended to be kept forever. So now to prove the eternity of the Mitzvos.
Five proofs for the eternity of the Mitzvos:
(1) Until otherwise proven, these Mosaic commandments are self-evidently eternal, unless the Torah would have clearly stated a time-limit. The burden-of-proof to change the established Word of G-d lies upon the ones intending to change it and no defense is technically even needed.
(2) Adjacent with many Mitzvos, the Torah uses the term “an everlasting statute for all generations.”[iv] In addition, see Numbers 15:22-23 where is encourages “… to do…all the commandments that G-d commanded you through Moses to do from the day he commanded it and onward.” Deuteronomy 5:26 also says the commandments are everlasting: “May they be of such mind, to revere Me and follow all of My commandments all the days, that it may go well with them and their children forever!” From Deuteronomy 29:28 it’s crystal-clear that the commandments are everlasting: “The hidden are for G-d and the open are for us and for our children forever, to do all these commandments of this Torah.” There’s also a law that forbids us from subtracting any Mitzvah:[v] “The Mitzvah that I command you today you must watch to do, do not add thereon nor subtract.”
(3) If G-d was indeed to retract His word for us to stop keeping the commandments, He would probably use His “Mass Revelation” tactic (discussed at length in chapter “The Mass Revelation” in Vol. 1 of The Rational Believer Series) as He did when revealing His Will to us with the “Old Testament.” He would do so in order to rule out skepticism.
(4) After describing the Jewish exile, the Torah continues forecasting the Ultimate Redemption.[vi] One of the pivotal features mentioned of the era is the performance of all Mitzvos: “And the Lord your G-d will circumcise your heart and the heart of the offspring, to love the Lord your G-d with all your heart and all your soul, so that you may live… And you will return to listen to the word of G-d and do all of His commandments that I command you today. Evidently, the Mosaic commandments couldn’t have expired prior this Messianic Era that has yet to occur.
Similarly, Ezekiel 36:26-27 mentions this circumcision of the stone heart (i.e. stubbornness) proceeded with the action of doing the commandments: “And I will give you a new heart and put a new spirit into you: I will remove the heart of stone from your body and give you a heart of flesh; and I will put My spirit into you. Thus I will cause you to follow My laws and faithfully to observe My rules.” 
[One might attempt to claim that these prophetic statements just mentioned of Deuteronomy 28 and 30 (which mention the performance of Mitzvos in that era) are only conditional, i.e. they would materialize only if the Jews would perfectly adhere to the Law and the “Mosaic Era” would continue. This argument, however, fails on two grounds. Firstly, G-d knows the future even before it materializes by our Free Will (this is clear from various Scriptures and is a logical conclusion). Thus, He wouldn’t unconditionally prophesy something which is not actually going to happen. Secondly, if you claim Deuteronomy 28 and 30 to only be conditional prophecies you bump into a huge problem: The curses of Deuteronomy 28 happened so clearly to the Jews throughout the past 2,000 years! The last step to unfold of the prophecies of Deuteronomy 28, which is in chapter 30, is thus bound to happen!]
(4) Moreover, we see in Zechariah[vii] that after the redemption we will still be performing the Mitzvah of Sukkos. But wasn’t the commandment of Sukkos, along with most of the other Mosaic Laws, abolished with the arrival of Jesus? We see from here that apparently not. 
 “To the Jews I became like a Jew, to win the Jews. To those under the law I became like one under the law (though I myself am not under the law), so as to win those under the law. 21 To those not having the law I became like one not having the law (though I am not free from God’s law but am under Christ’s law), so as to win those not having the law” (I Corinthians 9:20-21).
“Stand fast therefore in the liberty wherewith Christ hath made us free, and be not entangled again with the yoke of bondage. Behold, I Paul say unto you, that if ye be circumcised, Christ shall profit you nothing. For I testify again to every man that is circumcised, that he is a debtor to do the whole law. Christ is become of no effect unto you, whosoever of you are justified by the law; ye are fallen from grace. For we through the Spirit wait for the hope of righteousness by faith. For in Jesus Christ neither circumcision availeth any thing, nor uncircumcision; but faith which worketh by love.” (Galatians 5:2-6)
 Notice, that the Torah differentiates between “circumcision of the heart” and doing the action of the Mitzvos, indicating that belief in the heart doesn’t substitute the need for physically performing the command. Additionally, the circumcision will come from G-d (“and G-d shall circumcise…”) and the action of doing the commandments will come from the person (“and you will listen… to do all of the commandments…”).
 In a dialogue with missionary Dr. Michael Brown, he suggested an answer to my objection. He compared the Mosaic Laws to be like Yom Kippur which will apparently be abolished by the Redemption. The reason is because its whole purpose is to forgive the sins of the year, but by the Redemption our sins will either-way be forgiven, as prophesied all along the Prophets (e.g., Ezekiel 36:25-27). So, Yom Kippur is therefore similar to a command which only exists if certain circumstances exist, and in our case if the existence of a sin exists. So, technically the Mitzvah of Yom Kippur will exist by the Redemption if a sin will occur, but it’s just that the particular criteria will never end up being met because there will be no more sin.
The missionary then compared this same concept to all the Mosaic laws in the post-Jesus era. The Laws are intended to achieve a greater spiritual purpose. But after Jesus died at the Cross, there was no more the need to actually perform those Laws In order to achieve that spiritual purpose. Hence, the spiritual achievement is in a sense the “criteria” needed in order for the Mitzvah to apply. However, since the time of Jesus’ death, this “criteria” was no longer met because that spiritual achievement is already achieved by the virtue death of his. As a result, the Mosaic Laws no longer apply—not because they were abolished, but because their conditions are never met.
That is a good point made by the missionary but there is a counter-argument. The circumstance of Yom Kippur (i.e. the existence of sin) is a physical understandable circumstance. Additionally, its circumstance was clearly laid out in the Torah by G-d with no proof needed for it. On the other hand, this claim of the missionaries is a baseless claim, that although possible, has no support or basis for it. It is some “spiritual” circumstance, that for some reason was not laid out at all in the Torah, as was done by Yom Kippur. Consequently, the burden of proof is on the missionaries, and they fail to provide such evidence.
It’s like a king legislating many decrees by letter, and one decree is to pay tax “for the current war going on.” He ends off the letter by saying that these Laws are binding forever. Now obviously, if the war is to end then the additional tax is to drop—despite the end of the letter that the laws—as a whole—are forever binding. That is because one would rightfully understand this commandment to apply only if there’s the war—as the very commandment clearly laid out. But what if one is to come and claim that they are a messenger of the king and that a different law, a law that all citizens are to erect the countries national flag in their front lawn, is abolished because the whole reason of the law was just to enforce the idea of loyalty, but now we are loyal enough and don’t need it anymore (a criteria not mentioned anywhere by the actual commandment in the letter). I think it’s fair enough to suggest that anyone loyal to the king would not believe this claimed messenger of the king and abolish that commandment.
Alternatively, it can be argued that Yom Kippur will remain intact throughout the Messianic Age. Although there will be significantly less sin (both in quality and quantity—see e.g. Jeremiah 31:30-33), there still will be sin—on some level—even in the Messianic Age. For that, we will need Yom Kippur to pray for forgiveness and thus the aforesaid missionary’s argument is dismantled. [When the prophets speak of G-d forgiving our sins at the Messianic Age, it is referring to the sins that caused the exile. It is not for that Era. For those sins, repentance on Yom Kippur is indeed needed.]
 Any rabbinic literature from which it appears that some commandments will be abolished when the Messiah comes, is not to be taken literally but metaphorically. This is a known principle concerning many of the Aggadic teachings—see chapter “Did the Wild Stories of Midrash Actually Happen?” in Vol. 2 of The Rational Believer series. Many works have already been published in explanation of these Aggadic statements. If they were to be taken literally, I would indeed not believe in them based on the above Scriptural proofs.
There are some Christians, including Jewish Christians, who because of this chapter indeed celebrate some sort of “Sukkos.” The question is not as strong for such a person, but it still remains quite baffling for him why Sukkos, which is a typical Mosaic Law, would be different than the other Mosaic Laws that they claim are abolished.
[iii] Leviticus 11:7-8.
[iv] See Exodus 12:14-17, Leviticus 3:17, 16:29, 31, 23:21, 41 amongst more.
[v] Deuteronomy 4:2, 13:1.
[vi] Deuteronomy 30:1-10.